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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
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<title>Perl New Features and Foostats</title>
<link rel="shortcut icon" type="image/gif" href="/favicon.ico" />
<link rel="stylesheet" href="../style.css" />
<link rel="stylesheet" href="style-override.css" />
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<body>
<div class="rfx-overlay-grid"></div>
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<p class="header">
<a href="https://foo.zone">Home</a> | <a href="https://codeberg.org/snonux/foo.zone/src/branch/content-md/gemfeed/2025-11-02-perl-new-features-and-foostats.md">Markdown</a> | <a href="gemini://foo.zone/gemfeed/2025-11-02-perl-new-features-and-foostats.gmi">Gemini</a>
</p>
<h1 style='display: inline' id='perl-new-features-and-foostats'>Perl New Features and Foostats</h1><br />
<br />
<span class='quote'>Published at 2025-11-01T16:10:35+02:00</span><br />
<br />
<span>Perl recently reached rank 10 in the TIOBE index. That headline made me write this blog post as I was developing the Foostats script for simple analytics of my personal websites and Gemini capsules (e.g. <span class='inlinecode'>foo.zone</span>) and there were a couple of new features added to the Perl language over the last releases. The book *Perl New Features* by brian d foy documents the changes well; this post shows how those features look in a real program that runs every morning for my stats generation.</span><br />
<br />
<a class='textlink' href='https://developers.slashdot.org/story/25/09/14/0134239/is-perl-the-worlds-10th-most-popular-programming-language'>Perl re-enters the top ten</a><br />
<a class='textlink' href='https://perlschool.com/books/perl-new-features/'>Perl New Features by Joshua McAdams and brian d foy</a><br />
<br />
<pre>
$b="24P7cP3dP31P3bPaP28P24P64P31P2cP24P64P32P2cP24P73P2cP24P67P2cP24P7
2P29P3dP28P22P31P30P30P30P30P22P2cP22P31P30P30P30P30P30P22P2cP22P4aP75
P7 3P
74 P2
0P 41P6eP6fP74P 68P65P72P20P50 P65P72P6cP2 0P48P 61
P6 3P6bP65P72P22P 29P3bPaP40P6dP 3dP73P70P6cP6 9P74P 20
P2 fP2fP 2cP22P 2cP2eP3aP21P2 bP2aP 30P4f P40P2 2P
3b PaP24 P6eP3 dP6c P65P6 eP67 P74P6 8P
20 P24P7 3P3bP aP24 P75P3 dP22 P20P2 2P
78 P24P6 eP3bP aPaP 70P72 P69P 6eP74 P2
0P 22P5c P6eP20 P20P 24P75 P5cP7 2P22P 3b
Pa PaP66P6fP72P2 8P24P7aP20P 3dP20P31P3bP 20P24 P7
aP 3cP3dP24P6 eP3bP20P24 P7aP2bP2bP 29P20 P7
bP aPaP9 P77P28P24P6 4P31P29P 3bPaP 9P
24 P72P3 dP69 P6eP74P28 P72P6 1P
6e P64P2 8P24 P6eP2 9P29P 3bPaP 9P
24 P67P3 dP73 P75P6 2P73P 74P72 P2
0P 24P73 P2cP24P72P2cP 31P3b PaP9P 24P67P20P3fP20 P6
4P 6fP20 P9P7bP20PaP9P9 P9P9P 9P66P 6fP72P20P28P24 P6
bP 3dP30 P3bP24P6bP3cP3 9P3bP 24P6bP 2bP2bP29P20P7b Pa
P9 P9
P9 P9
P9 P9P73P75P6 2P73 P74P 72P2 8P24P75P2c P24P72 P2
cP 31P29P3dP24P 6dP5 bP24 P6bP 5dP3bP20Pa P9P9 P9P9 P9
P9 P70P 72P69 P6eP 74P2 0P22 P20P20P24P 75P 5cP 72
P2 2P3b PaP9 P9P9 P9P9 P9P7 7P28 P24 P6 4P
32 P29P 3bPa P9P9 P9P9 P9P7 dPaP 9P9 P9
P9 P9P7 3P75 P62P 73P7 4P72 P28P 24P7 5P
2c P24P 72P2c P31P 29P3 dP24 P67P3bP20P aP9P9 P9
P9 P7dP20PaP9P 9P3a P20P 72P6 5P64P6fP3b PaP9 P7
3P 75P62P73P 74P7 2P28 P24P 73P2cP24P7 2P2c P3
1P 29P3dP2 2P30 P22P 3bPa P9P7 0P7 2P
69 P6eP74P2 0P22 P20P 20P2 4P75 P5c P7
2P 22P3 bPaPa P7dP aPaP 77P2 0P28 P24 P6
4P 32P2 9P3bP aP70 P72P 69P6 eP74 P2 0P2 2P
20 P20P 24P75 P20P21P5cP7 2P22P3bPaP 73P6cP65P6 5P7 0P20 P3
2P 3bPa P70P7 2P69P6eP74P 20P22P20P2 0P24P75P20 P21P 5cP6 eP
22 P3bP aPaP7 3P75P62P2 0P77P20P7b PaP9P24P6c P3dP73 P6
8P 69
P6 6P
74P3bPaP9P66P6fP72P28P24P6aP3dP30P3bP24P6aP3cP24P6cP3bP24P6aP2bP2bP29P
7bP7dPaP7dP";$b=~s/\s//g;split /P/,$b;foreach(@_){$c.=chr hex};eval $c
The above Perl script prints out "Just Another Perl Hacker !" in an
animation of sorts.
</pre>
<br />
<h2 style='display: inline' id='table-of-contents'>Table of Contents</h2><br />
<br />
<ul>
<li><a href='#perl-new-features-and-foostats'>Perl New Features and Foostats</a></li>
<li>⇢ <a href='#motivation'>Motivation</a></li>
<li>⇢ <a href='#why-i-used-perl'>Why I used Perl</a></li>
<li>⇢ <a href='#inside-foostats'>Inside Foostats</a></li>
<li>⇢ ⇢ <a href='#log-pipeline'>Log pipeline</a></li>
<li>⇢ ⇢ <a href='#foooddstxt'><span class='inlinecode'>fooodds.txt</span></a></li>
<li>⇢ ⇢ <a href='#feed-kinds'>Feed kinds</a></li>
<li>⇢ ⇢ <a href='#aggregation-and-output'>Aggregation and output</a></li>
<li>⇢ ⇢ <a href='#command-line-entry-points'>Command-line entry points</a></li>
<li>⇢ <a href='#packages-as-real-blocks'>Packages as real blocks</a></li>
<li>⇢ ⇢ <a href='#scoped-packages'>Scoped packages</a></li>
<li>⇢ <a href='#postfix-dereferencing-keeps-data-structures-tidy'>Postfix dereferencing keeps data structures tidy</a></li>
<li>⇢ ⇢ <a href='#clear-dereferencing'>Clear dereferencing</a></li>
<li>⇢ <a href='#say-is-the-default-voice-now'><span class='inlinecode'>say</span> is the default voice now</a></li>
<li>⇢ <a href='#lexical-subs-promote-local-reasoning'>Lexical subs promote local reasoning</a></li>
<li>⇢ <a href='#reference-aliasing-makes-intent-explicit'>Reference aliasing makes intent explicit</a></li>
<li>⇢ <a href='#persistent-state-without-globals'>Persistent state without globals</a></li>
<li>⇢ ⇢ <a href='#rate-limiting-state'>Rate limiting state</a></li>
<li>⇢ ⇢ <a href='#de-duplicated-logging'>De-duplicated logging</a></li>
<li>⇢ <a href='#subroutine-signatures'>Subroutine signatures</a></li>
<li>⇢ <a href='#defined-or-assignment-for-defaults-without-boilerplate'>Defined-or assignment for defaults without boilerplate</a></li>
<li>⇢ <a href='#cleanup-with-defer'>Cleanup with <span class='inlinecode'>defer</span></a></li>
<li>⇢ <a href='#builtins-and-booleans'>Builtins and booleans</a></li>
<li>⇢ <a href='#conclusion'>Conclusion</a></li>
</ul><br />
<h2 style='display: inline' id='motivation'>Motivation</h2><br />
<br />
<span>I've been running <span class='inlinecode'>foo.zone</span> for a while now, but I've never looked into visitor statistics or analytics. I value privacy—not just my own, but also the privacy of others (the visitors of this site) — so I hesitated to use any off-the-shelf analytics plugins. All I wanted to collect were:</span><br />
<br />
<ul>
<li>Which blog posts had the most (unique) visitors</li>
<li>Exclude, if possible, any bots and scrapers from the stats</li>
<li>Track only anonymized IP addresses, never store raw addresses</li>
</ul><br />
<span>With Foostats I've created a Perl script which does that for my highly opinionated website/blog setup, which consists of:</span><br />
<br />
<a class='textlink' href='https://foo.zone/gemfeed/2021-06-05-gemtexter-one-bash-script-to-rule-it-all.html'>Gemtexter, my static site and Gemini capsule generator</a><br />
<a class='textlink' href='https://foo.zone/gemfeed/2024-04-01-KISS-high-availability-with-OpenBSD.html'>How I host this site highly-available using OpenBSD</a><br />
<br />
<h2 style='display: inline' id='why-i-used-perl'>Why I used Perl</h2><br />
<br />
<span>Even though nowadays I code more in Go and Ruby, I stuck with Perl for Foostats for four simple reasons:</span><br />
<br />
<ul>
<li>I wanted an excuse to explore the newer features of my first programming love.</li>
<li>Sometimes, I miss Perl.</li>
<li>Perl ships with OpenBSD (the operating system on which my sites run) by default.</li>
<li>It really does live up to its Practical Extraction and Report Language (that's what the name Perl means) for this kind of log grinding I did with Foostats.</li>
</ul><br />
<h2 style='display: inline' id='inside-foostats'>Inside Foostats</h2><br />
<br />
<span>Foostats is simply a log file analyser, which analyses the OpenBSD httpd and relayd logs.</span><br />
<br />
<a class='textlink' href='https://man.openbsd.org/httpd.8'>https://man.openbsd.org/httpd.8</a><br />
<a class='textlink' href='https://man.openbsd.org/relayd.8'>https://man.openbsd.org/relayd.8</a><br />
<br />
<h3 style='display: inline' id='log-pipeline'>Log pipeline</h3><br />
<br />
<span>A CRON job starts Foostats, reads OpenBSD httpd and relayd access logs, and produces the numbers published at <span class='inlinecode'>https://stats.foo.zone</span> and <span class='inlinecode'>gemini://stats.foo.zone</span>. The dashboards are humble because traffic on my sites is still light, yet the trends are interesting for spotting patterns. The script is opinionated (I am repeating myself here, I know), and I will probably be the only one ever using it for my own sites. However, the code demonstrates how Perl's newer features help keep a small script like this exciting and fun!</span><br />
<br />
<a class='textlink' href='https://stats.foo.zone'>Foostats (HTTP)</a><br />
<a class='textlink' href='gemini://stats.foo.zone'>Foostats (Gemini)</a><br />
<br />
<span>On OpenBSD, I've configured the job via the <span class='inlinecode'>daily.local</span> on both of my OpenBSD servers (<span class='inlinecode'>fishfinger.buetow.org</span> and <span class='inlinecode'>blowfish.buetow.org</span> - note one is the master server, the other is the standby server, but the script runs on both and the stats are merged later in the process):</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><font color="#ff0000">fishfinger$ grep foostats /etc/daily</font><font color="#F3E651">.</font><b><font color="#ffffff">local</font></b>
<font color="#ff0000">perl /usr/local/bin/foostats</font><font color="#F3E651">.</font><font color="#ff0000">pl --parse-logs --replicate --report</font>
</pre>
<br />
<span>Internally, <span class='inlinecode'>Foostats::Logreader</span> parses each line of the log files <span class='inlinecode'>/var/log/daemon*</span> and <span class='inlinecode'>/var/www/logs/access_log*</span>, turns timestamps into <span class='inlinecode'>YYYYMMDD/HHMMSS</span> values, hashes IP addresses with SHA3 (for anonymization), and hands a normalized event to <span class='inlinecode'>Foostats::Filter</span>. The filter compares the URI against entries in <span class='inlinecode'>fooodds.txt</span>, tracks how many times an IP address requests within the exact second, and drops anything suspicious (e.g., from web crawlers or malicious attackers). Valid events reach <span class='inlinecode'>Foostats::Aggregator</span>, which counts requests per protocol, records unique visitors for the Gemtext and Atom feeds, and remembers page-level IP sets. <span class='inlinecode'>Foostats::FileOutputter</span> writes the result as gzipped JSON files—one per day and per protocol—with IPv4/IPv6 splits, filtered counters, feed readership, and hashes for long URLs.</span><br />
<br />
<h3 style='display: inline' id='foooddstxt'><span class='inlinecode'>fooodds.txt</span></h3><br />
<br />
<span><span class='inlinecode'>fooodds.txt</span> is a plain text list of substrings of URLs to be blocked, making it quick to shut down web crawlers. Foostats also detects rapid requests (an indicator of excessive crawling) and blocks the IP. Audit lines are written to <span class='inlinecode'>/var/log/fooodds</span>, which can later be reviewed for false or true positives (I do this around once a month). The <span class='inlinecode'>Justfile</span> even has a <span class='inlinecode'>gather-fooodds</span> target that collects suspicious paths from remote logs so new patterns can be added quickly.</span><br />
<br />
<h3 style='display: inline' id='feed-kinds'>Feed kinds</h3><br />
<br />
<span>There are different kinds of feeds being tracked by Foostats:</span><br />
<br />
<ul>
<li>The Atom web-feed</li>
<li>The same feed via Gemini</li>
<li>The Gemfeed (a special format popular in the Geminispace)</li>
</ul><br />
<h3 style='display: inline' id='aggregation-and-output'>Aggregation and output</h3><br />
<br />
<span>As mentioned, Foostats merges the stats from both hosts, master and standby. For the master-standby setup description, read:</span><br />
<br />
<a class='textlink' href='./2024-04-01-KISS-high-availability-with-OpenBSD.html'>KISS high-availability with OpenBSD</a><br />
<br />
<span>Those gzipped files land in <span class='inlinecode'>stats/</span>. From there, <span class='inlinecode'>Foostats::Replicator</span> can pull matching files from the partner host (<span class='inlinecode'>fishfinger</span> or <span class='inlinecode'>blowfish</span>) so the view covers both servers, <span class='inlinecode'>Foostats::Merger</span> combines them into daily summaries, and <span class='inlinecode'>Foostats::Reporter</span> rebuilds Gemtext and HTML reports.</span><br />
<br />
<span>Those are the raw stats files:</span><br />
<br />
<a class='textlink' href='https://blowfish.buetow.org/foostats/'>https://blowfish.buetow.org/foostats/</a><br />
<a class='textlink' href='https://fishfinger.buetow.org/foostats/'>https://fishfinger.buetow.org/foostats/</a><br />
<br />
<span>These are the 30-day reports generated (already linked earlier in this post, but adding here again for clarity):</span><br />
<br />
<a class='textlink' href='gemini://stats.foo.zone'>stats.foo.zone Gemini capsule dashboard</a><br />
<a class='textlink' href='https://stats.foo.zone'>stats.foo.zone HTTP dashboard</a><br />
<br />
<h3 style='display: inline' id='command-line-entry-points'>Command-line entry points</h3><br />
<br />
<span><span class='inlinecode'>foostats_main</span> is the command entry point. <span class='inlinecode'>--parse-logs</span> refreshes the gzipped files, <span class='inlinecode'>--replicate</span> runs the cross-host sync, and <span class='inlinecode'>--report</span> rebuilds the HTML and Gemini report pages. <span class='inlinecode'>--all</span> performs everything in one go. Defaults point to <span class='inlinecode'>/var/www/htdocs/buetow.org/self/foostats</span> for data, <span class='inlinecode'>/var/gemini/stats.foo.zone</span> for Gemtext output, and <span class='inlinecode'>/var/www/htdocs/gemtexter/stats.foo.zone</span> for HTML output. Replication always forces the three most recent days' worth of data across HTTPS and leaves older files untouched to save bandwidth.</span><br />
<br />
<span>The complete source lives on Codeberg here:</span><br />
<br />
<a class='textlink' href='https://codeberg.org/snonux/foostats'>Foostats on Codeberg</a><br />
<br />
<span>Now let's go to some new Perl features:</span><br />
<br />
<h2 style='display: inline' id='packages-as-real-blocks'>Packages as real blocks</h2><br />
<br />
<h3 style='display: inline' id='scoped-packages'>Scoped packages</h3><br />
<br />
<span>Recent Perl versions allow the block form <span class='inlinecode'>package Foo { ... }</span>. Foostats uses it for every package. Imports stay local to the block, helper subs do not leak into the global symbol table, and configuration happens where the code needs it.</span><br />
<br />
<span>The old way:</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><b><font color="#ffffff">package</font></b><font color="#ff0000"> foo</font><font color="#F3E651">;</font>
<b><font color="#ffffff">sub</font></b><font color="#ff0000"> hello </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#bb00ff">"Hello from package foo\n"</font><font color="#F3E651">;</font>
<font color="#F3E651">}</font>
<b><font color="#ffffff">package</font></b><font color="#ff0000"> bar</font><font color="#F3E651">;</font>
<b><font color="#ffffff">sub</font></b><font color="#ff0000"> hello </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#bb00ff">"Hello from package bar\n"</font><font color="#F3E651">;</font>
<font color="#F3E651">}</font>
</pre>
<br />
<span>But now it is also possible to do this:</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><b><font color="#ffffff">package</font></b><font color="#ff0000"> foo </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">sub</font></b><font color="#ff0000"> hello </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#bb00ff">"Hello from package foo\n"</font><font color="#F3E651">;</font>
<font color="#ff0000"> </font><font color="#F3E651">}</font>
<font color="#F3E651">}</font>
<b><font color="#ffffff">package</font></b><font color="#ff0000"> bar </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">sub</font></b><font color="#ff0000"> hello </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#bb00ff">"Hello from package bar\n"</font><font color="#F3E651">;</font>
<font color="#ff0000"> </font><font color="#F3E651">}</font>
<font color="#F3E651">}</font>
</pre>
<br />
<h2 style='display: inline' id='postfix-dereferencing-keeps-data-structures-tidy'>Postfix dereferencing keeps data structures tidy</h2><br />
<br />
<h3 style='display: inline' id='clear-dereferencing'>Clear dereferencing</h3><br />
<br />
<span>The script handles nested hashes and arrays. Postfix dereferencing (<span class='inlinecode'>$hash->%*</span>, <span class='inlinecode'>$array->@*</span>) keeps that readable.</span><br />
<br />
<span>E.g. instead of having to write:</span><br />
<br />
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<pre><b><font color="#ffffff">for</font></b><font color="#ff0000"> </font><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$elem</font><font color="#ff0000"> </font><font color="#F3E651">(</font><font color="#ff0000">@</font><font color="#F3E651">{</font><font color="#ff0000">$array_ref</font><font color="#F3E651">}</font><font color="#F3E651">)</font><font color="#ff0000"> </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#bb00ff">"$elem\n"</font><font color="#F3E651">;</font>
<font color="#F3E651">}</font>
</pre>
<br />
<span>one can now do:</span><br />
<br />
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<pre><b><font color="#ffffff">for</font></b><font color="#ff0000"> </font><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$elem</font><font color="#ff0000"> </font><font color="#F3E651">(</font><font color="#ff0000">$array_ref</font><font color="#F3E651">-></font><font color="#ff0000">@</font><font color="#F3E651">*)</font><font color="#ff0000"> </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#bb00ff">"$elem\n"</font><font color="#F3E651">;</font>
<font color="#F3E651">}</font>
</pre>
<br />
<span>You see that this feature becomes increasingly useful with nested data structures, e.g. to print all keys of the nested hash:</span><br />
<br />
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<pre><b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><b><font color="#ffffff">for</font></b><font color="#ff0000"> </font><b><font color="#ffffff">keys</font></b><font color="#ff0000"> </font><font color="#ff0000">$hash</font><font color="#F3E651">-></font><font color="#F3E651">{</font><font color="#ff0000">stats</font><font color="#F3E651">}</font><font color="#F3E651">->%*;</font>
</pre>
<br />
<span>Loops over like <span class='inlinecode'>$stats->{page_ips}->{urls}->%*</span> or <span class='inlinecode'>$merge{$key}->{$_}->%*</span> show which level of the structure is in play. The merger in Foostats updates host and URL statistics without building temporary arrays, and the reporter code mirrors the layout of the final tables. Before postfix dereferencing, the same code relied on braces within braces and was harder to read.</span><br />
<br />
<h2 style='display: inline' id='say-is-the-default-voice-now'><span class='inlinecode'>say</span> is the default voice now</h2><br />
<br />
<span><span class='inlinecode'>say</span> became the default once the script switched to <span class='inlinecode'>use v5.38;</span>. It adds a newline to every message printed, comparable to Ruby's <span class='inlinecode'>puts</span>, making log messages like "Processing $path" or "Writing report to $report_path" cleaner:</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
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<pre><b><font color="#ffffff">use</font></b><font color="#ff0000"> v5</font><font color="#F3E651">.</font><font color="#bb00ff">38</font><font color="#F3E651">;</font>
<b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#bb00ff">"Hello, world!\n"</font><font color="#F3E651">;</font><font color="#ff0000"> </font><i><font color="#ababab"># old way</font></i>
<font color="#ff0000">say </font><font color="#bb00ff">"Hello, world!"</font><font color="#F3E651">;</font><font color="#ff0000"> </font><i><font color="#ababab"># new way</font></i>
</pre>
<br />
<h2 style='display: inline' id='lexical-subs-promote-local-reasoning'>Lexical subs promote local reasoning</h2><br />
<br />
<span>Lexical subroutines keep helpers close to the code that needs them. In <span class='inlinecode'>Foostats::Logreader::parse_web_logs</span>, functions such as <span class='inlinecode'>my sub parse_date</span> and <span class='inlinecode'>my sub open_file</span> live only inside that scope.</span><br />
<br />
<span>This is an example of a lexical sub named <span class='inlinecode'>trim</span>, which is only visible within the outer sub named <span class='inlinecode'>process_lines</span>:</span><br />
<br />
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<pre><b><font color="#ffffff">use</font></b><font color="#ff0000"> v5</font><font color="#F3E651">.</font><font color="#bb00ff">38</font><font color="#F3E651">;</font>
<b><font color="#ffffff">sub</font></b><font color="#ff0000"> </font><font color="#7bc710">process_lines</font><font color="#ff0000"> </font><font color="#F3E651">(</font><font color="#ff0000">@lines</font><font color="#F3E651">)</font><font color="#ff0000"> </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><b><font color="#ffffff">sub</font></b><font color="#ff0000"> </font><font color="#7bc710">trim</font><font color="#ff0000"> </font><font color="#F3E651">(</font><font color="#ff0000">$str</font><font color="#F3E651">)</font><font color="#ff0000"> </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><font color="#ff0000">$str</font><font color="#ff0000"> </font><font color="#F3E651">=~</font><font color="#ff0000"> </font><b><font color="#ffffff">s</font></b><font color="#bb00ff">/^\s+|\s+$//</font><font color="#ff0000">gr</font><font color="#F3E651">;</font>
<font color="#ff0000"> </font><font color="#F3E651">}</font>
<font color="#ff0000"> </font><b><font color="#ffffff">return</font></b><font color="#ff0000"> </font><font color="#F3E651">[</font><font color="#ff0000"> </font><b><font color="#ffffff">map</font></b><font color="#ff0000"> </font><font color="#F3E651">{</font><font color="#ff0000"> </font><font color="#7bc710">trim</font><font color="#F3E651">(</font><font color="#ff0000">$_</font><font color="#F3E651">)</font><font color="#ff0000"> </font><font color="#F3E651">}</font><font color="#ff0000"> </font><font color="#ff0000">@lines</font><font color="#ff0000"> </font><font color="#F3E651">];</font>
<font color="#F3E651">}</font>
<b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">@raw</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><font color="#F3E651">(</font><font color="#bb00ff">" foo "</font><font color="#F3E651">,</font><font color="#ff0000"> </font><font color="#bb00ff">" bar"</font><font color="#F3E651">,</font><font color="#ff0000"> </font><font color="#bb00ff">"baz "</font><font color="#F3E651">);</font>
<b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$cleaned</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><font color="#7bc710">process_lines</font><font color="#F3E651">(</font><font color="#ff0000">@raw</font><font color="#F3E651">);</font>
<font color="#ff0000">say </font><b><font color="#ffffff">for</font></b><font color="#ff0000"> @</font><font color="#ff0000">$cleaned</font><font color="#F3E651">;</font><font color="#ff0000"> </font><i><font color="#ababab"># prints "foo", "bar", "baz"</font></i>
</pre>
<br />
<h2 style='display: inline' id='reference-aliasing-makes-intent-explicit'>Reference aliasing makes intent explicit</h2><br />
<br />
<span>Reference aliasing can be enabled with <span class='inlinecode'>use feature qw(refaliasing)</span> and helps communicate intent more clearly (if you remember the Perl syntax, of course—otherwise, it can look rather cryptic). The filter starts with <span class='inlinecode'>\my $uri_path = \$event->{uri_path}</span> so any later modification touches the original event. This is an example with ref aliasing in action:</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
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<pre><b><font color="#ffffff">use</font></b><font color="#ff0000"> feature </font><b><font color="#ffffff">qw</font></b><font color="#F3E651">(</font><font color="#ff0000">refaliasing</font><font color="#F3E651">);</font>
<b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$hash</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><font color="#F3E651">{</font><font color="#ff0000"> foo </font><font color="#F3E651">=></font><font color="#ff0000"> </font><font color="#bb00ff">42</font><font color="#ff0000"> </font><font color="#F3E651">}</font><font color="#F3E651">;</font>
<font color="#F3E651">\</font><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$foo</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><font color="#F3E651">\</font><font color="#ff0000">$hash</font><font color="#F3E651">-></font><font color="#F3E651">{</font><font color="#ff0000">foo</font><font color="#F3E651">}</font><font color="#F3E651">;</font>
<font color="#ff0000">$foo</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><font color="#bb00ff">99</font><font color="#F3E651">;</font>
<b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#ff0000">$hash</font><font color="#F3E651">-></font><font color="#F3E651">{</font><font color="#ff0000">foo</font><font color="#F3E651">}</font><font color="#F3E651">;</font><font color="#ff0000"> </font><i><font color="#ababab"># prints 99</font></i>
</pre>
<br />
<span>The aggregator in Foostats aliases <span class='inlinecode'>$self->{stats}{$date_key}</span> before updating counters, so the structure remains intact. Combined with subroutine signatures, this makes it obvious when a piece of data is shared instead of copied, preventing silent bugs. This enables having shorter names for long nested data structures.</span><br />
<br />
<h2 style='display: inline' id='persistent-state-without-globals'>Persistent state without globals</h2><br />
<br />
<span>A Perl state variable is declared with <span class='inlinecode'>state $var</span> and retains its value between calls to the enclosing subroutine. Foostats uses that for rate limiting and de-duplicated logging.</span><br />
<br />
<span>This is a small example demonstrating the use of a state variable in Perl:</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
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<pre><b><font color="#ffffff">sub</font></b><font color="#ff0000"> counter </font><font color="#F3E651">{</font>
<font color="#ff0000"> state </font><font color="#ff0000">$count</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><font color="#bb00ff">0</font><font color="#F3E651">;</font>
<font color="#ff0000"> </font><font color="#ff0000">$count</font><font color="#F3E651">++;</font>
<font color="#ff0000"> </font><b><font color="#ffffff">return</font></b><font color="#ff0000"> </font><font color="#ff0000">$count</font><font color="#F3E651">;</font>
<font color="#F3E651">}</font>
<font color="#ff0000">say </font><font color="#7bc710">counter</font><font color="#F3E651">();</font><font color="#ff0000"> </font><i><font color="#ababab"># 1</font></i>
<font color="#ff0000">say </font><font color="#7bc710">counter</font><font color="#F3E651">();</font><font color="#ff0000"> </font><i><font color="#ababab"># 2</font></i>
<font color="#ff0000">say </font><font color="#7bc710">counter</font><font color="#F3E651">();</font><font color="#ff0000"> </font><i><font color="#ababab"># 3</font></i>
</pre>
<br />
<span>Hash and array state variables have been supported since <span class='inlinecode'>state</span> arrived in Perl 5.10. Scalar state variables were already supported previously.</span><br />
<br />
<h3 style='display: inline' id='rate-limiting-state'>Rate limiting state</h3><br />
<br />
<span>In Foostats, <span class='inlinecode'>state</span> variables store run-specific state without using package globals. <span class='inlinecode'>state %blocked</span> remembers IP hashes that already triggered the odd-request filter, and <span class='inlinecode'>state $last_time</span> and <span class='inlinecode'>state %count</span> track how many requests an IP makes in the exact second.</span><br />
<br />
<h3 style='display: inline' id='de-duplicated-logging'>De-duplicated logging</h3><br />
<br />
<span><span class='inlinecode'>state %dedup</span> keeps the log output of the suspicious calls to one warning per URI. Early versions utilized global hashes for the same tasks, producing inconsistent results during tests. Switching to <span class='inlinecode'>state</span> removed those edge cases.</span><br />
<br />
<h2 style='display: inline' id='subroutine-signatures'>Subroutine signatures</h2><br />
<br />
<span>Perl now supports subroutine signatures like other modern languages do. Foostats uses them everywhere. Examples:</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
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http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><i><font color="#ababab"># Old way</font></i>
<b><font color="#ffffff">sub</font></b><font color="#ff0000"> greet_old </font><font color="#F3E651">{</font><font color="#ff0000"> </font><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$name</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><b><font color="#ffffff">shift</font></b><font color="#F3E651">;</font><font color="#ff0000"> </font><b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#bb00ff">"Hello, $name!\n"</font><font color="#ff0000"> </font><font color="#F3E651">}</font>
<i><font color="#ababab"># Another old way</font></i>
<b><font color="#ffffff">sub</font></b><font color="#ff0000"> </font><font color="#7bc710">greet_old2</font><font color="#ff0000"> </font><font color="#F3E651">(</font><font color="#ff0000">$</font><font color="#F3E651">)</font><font color="#ff0000"> </font><font color="#F3E651">{</font><font color="#ff0000"> </font><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$name</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><b><font color="#ffffff">shift</font></b><font color="#F3E651">;</font><font color="#ff0000"> </font><b><font color="#ffffff">print</font></b><font color="#ff0000"> </font><font color="#bb00ff">"Hello, $name!\n"</font><font color="#ff0000"> </font><font color="#F3E651">}</font>
<i><font color="#ababab"># New way</font></i>
<b><font color="#ffffff">sub</font></b><font color="#ff0000"> </font><font color="#7bc710">greet</font><font color="#ff0000"> </font><font color="#F3E651">(</font><font color="#ff0000">$name</font><font color="#F3E651">)</font><font color="#ff0000"> </font><font color="#F3E651">{</font><font color="#ff0000"> say </font><font color="#bb00ff">"Hello, $name!"</font><font color="#F3E651">;</font><font color="#ff0000"> </font><font color="#F3E651">}</font>
<font color="#7bc710">greet</font><font color="#F3E651">(</font><font color="#bb00ff">"Alice"</font><font color="#F3E651">);</font><font color="#ff0000"> </font><i><font color="#ababab"># prints "Hello, Alice!"</font></i>
</pre>
<br />
<span>In Foostats, constructors declare <span class='inlinecode'>sub new ($class, $odds_file, $log_path)</span>, anonymous callbacks expose <span class='inlinecode'>sub ($event)</span>, and helper subs list the values they expect, e.g.:</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$anon</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><b><font color="#ffffff">sub</font></b><font color="#ff0000"> </font><font color="#F3E651">(</font><font color="#ff0000">$name</font><font color="#F3E651">)</font><font color="#ff0000"> </font><font color="#F3E651">{</font>
<font color="#ff0000"> say </font><font color="#bb00ff">"Hello, $name!"</font><font color="#F3E651">;</font>
<font color="#F3E651">}</font><font color="#F3E651">;</font>
<font color="#ff0000">$anon</font><font color="#F3E651">->(</font><font color="#bb00ff">"World"</font><font color="#F3E651">);</font><font color="#ff0000"> </font><i><font color="#ababab"># prints "Hello, World!"</font></i>
</pre>
<br />
<h2 style='display: inline' id='defined-or-assignment-for-defaults-without-boilerplate'>Defined-or assignment for defaults without boilerplate</h2><br />
<br />
<span>The operator <span class='inlinecode'>//=</span> keeps configuration and counters simple. Environment variables may be missing when CRON runs the script, so <span class='inlinecode'>//=</span>, combined with signatures, sets defaults without warnings. Example use of that operator:</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$foo</font><font color="#F3E651">;</font>
<font color="#ff0000">$foo</font><font color="#ff0000"> </font><font color="#bb00ff">//</font><font color="#F3E651">=</font><font color="#ff0000"> </font><font color="#bb00ff">42</font><font color="#F3E651">;</font>
<font color="#ff0000">say </font><font color="#ff0000">$foo</font><font color="#F3E651">;</font><font color="#ff0000"> </font><i><font color="#ababab"># prints 42</font></i>
<font color="#ff0000">$foo</font><font color="#ff0000"> </font><font color="#bb00ff">//</font><font color="#F3E651">=</font><font color="#ff0000"> </font><font color="#bb00ff">99</font><font color="#F3E651">;</font>
<font color="#ff0000">say </font><font color="#ff0000">$foo</font><font color="#F3E651">;</font><font color="#ff0000"> </font><i><font color="#ababab"># still prints 42, because $foo was already defined</font></i>
</pre>
<br />
<h2 style='display: inline' id='cleanup-with-defer'>Cleanup with <span class='inlinecode'>defer</span></h2><br />
<br />
<span>Even though not used in Foostats, this feature (similar to Go's defer) is neat to have in Perl now.</span><br />
<br />
<span>The <span class='inlinecode'>defer</span> block (<span class='inlinecode'>use feature 'defer"</span>) schedules a piece of code to run when the current scope exits, regardless of how it exits (e.g. normal return, exception). This is perfect for ensuring resources, such as file handles, are closed.</span><br />
<br />
<!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><b><font color="#ffffff">use</font></b><font color="#ff0000"> feature </font><b><font color="#ffffff">qw</font></b><font color="#F3E651">(</font><font color="#ff0000">defer</font><font color="#F3E651">);</font>
<b><font color="#ffffff">sub</font></b><font color="#ff0000"> </font><font color="#7bc710">parse_log_file</font><font color="#ff0000"> </font><font color="#F3E651">(</font><font color="#ff0000">$path</font><font color="#F3E651">)</font><font color="#ff0000"> </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><b><font color="#ffffff">open</font></b><font color="#ff0000"> </font><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$fh</font><font color="#F3E651">,</font><font color="#ff0000"> </font><font color="#bb00ff">'<'</font><font color="#F3E651">,</font><font color="#ff0000"> </font><font color="#ff0000">$path</font><font color="#ff0000"> or </font><b><font color="#ffffff">die</font></b><font color="#ff0000"> </font><font color="#bb00ff">"Cannot open $path: $!"</font><font color="#F3E651">;</font>
<font color="#ff0000"> defer </font><font color="#F3E651">{</font><font color="#ff0000"> </font><b><font color="#ffffff">close</font></b><font color="#ff0000"> </font><font color="#ff0000">$fh</font><font color="#ff0000"> </font><font color="#F3E651">}</font><font color="#F3E651">;</font>
<font color="#ff0000"> </font><b><font color="#ffffff">while</font></b><font color="#ff0000"> </font><font color="#F3E651">(</font><b><font color="#ffffff">my</font></b><font color="#ff0000"> </font><font color="#ff0000">$line</font><font color="#ff0000"> </font><font color="#F3E651">=</font><font color="#ff0000"> </font><font color="#bb00ff"><$fh></font><font color="#F3E651">)</font><font color="#ff0000"> </font><font color="#F3E651">{</font>
<font color="#ff0000"> </font><i><font color="#ababab"># ... parsing logic that might throw an exception ...</font></i>
<font color="#ff0000"> </font><font color="#F3E651">}</font>
<font color="#ff0000"> </font><i><font color="#ababab"># $fh is automatically closed here</font></i>
<font color="#F3E651">}</font>
</pre>
<br />
<span>This pattern replaces manual <span class='inlinecode'>close</span> calls in every exit path of the subroutine and is more robust than relying solely on object destructors.</span><br />
<br />
<h2 style='display: inline' id='builtins-and-booleans'>Builtins and booleans</h2><br />
<br />
<span>The script also utilizes other modern additions that often go unnoticed. <span class='inlinecode'>use builtin qw(true false);</span> combined with <span class='inlinecode'>experimental::builtin</span> provides more real boolean values.</span><br />
<br />
<h2 style='display: inline' id='conclusion'>Conclusion</h2><br />
<br />
<span>I want to code more in Perl again. The newer features make it a joy to write small scripts like Foostats. If you haven't looked at Perl in a while, give it another try! The main thing which holds me back from writing more Perl is the lack of good tooling. For example, there is no proper LSP and tree sitter support available, which would work as good as the ones available for Go and Ruby.</span><br />
<br />
<span class='quote'>A reader pointed out that there's now a third-party Perl Tree-sitter implementation one could use:</span><br />
<br />
<a class='textlink' href='https://github.com/tree-sitter-perl/tree-sitter-perl'>https://github.com/tree-sitter-perl/tree-sitter-perl</a><br />
<br />
<span>E-Mail your comments to <span class='inlinecode'>paul@nospam.buetow.org</span> :-)</span><br />
<br />
<span>Other related posts are:</span><br />
<br />
<a class='textlink' href='./2025-11-02-perl-new-features-and-foostats.html'>2025-11-02 Perl New Features and Foostats (You are currently reading this)</a><br />
<a class='textlink' href='./2023-05-01-unveiling-guprecords:-uptime-records-with-raku.html'>2023-05-01 Unveiling <span class='inlinecode'>guprecords.raku</span>: Global Uptime Records with Raku</a><br />
<a class='textlink' href='./2022-05-27-perl-is-still-a-great-choice.html'>2022-05-27 Perl is still a great choice</a><br />
<a class='textlink' href='./2011-05-07-perl-daemon-service-framework.html'>2011-05-07 Perl Daemon (Service Framework)</a><br />
<a class='textlink' href='./2008-06-26-perl-poetry.html'>2008-06-26 Perl Poetry</a><br />
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