feat: Add hyper operator methods for stack operations

- Added HyperAdd, HyperMultiply, HyperSubtract, HyperDivide, HyperPower, HyperModulo
- Each hyper operator pops all values from stack and applies left-associative operation
- Updated token evaluation to recognize [op] pattern (e.g., [+], [-], [*], [/], [^], [%])
- Added comprehensive test cases for all hyper operators
- Updated README.md with hyper operator documentation and fixed persistent RPN state notes

Hyper operators allow operating on all stack values at once, while regular operators
work on the top two values.

1 files changed, 34 insertions, 6 deletions

diff --git a/README.md b/README.md
index 15571d9..ac0ab65 100644
--- a/README.md
+++ b/README.md
@@ -136,19 +136,47 @@ perc calc 1 2 3 show      # Show stack without modifying
 
 ### REPL Mode Notes
 
-In REPL mode, each line is evaluated independently. To chain operations:
-- Use the `rpn` subcommand for multi-step expressions: `rpn 2 3 + 4 -`
-- Or use the `rpn` command to set variables: `rpn x 5 =` then `rpn x x +`
-- The `show` command can display the final stack state
+In REPL mode, RPN operations maintain persistent state between commands. This allows you to build up values on the stack across multiple commands.
 
 Example REPL session:
 ```
 perc> rpn 2 3 4 +        # Push 2, 3, 4; add last two
 2 7
-perc> rpn show           # Show full stack (but we start fresh per command)
+perc> +                  # Add top two: 2 + 7 = 9
+9
+perc> 5 *                # Multiply by 5: 9 * 5 = 45
+45
 ```
 
-Note: Each REPL command is evaluated independently, so you cannot chain operations like `2 3 4 +` then `-` on separate lines. Use `rpn 2 3 4 + -` for a single expression instead.
+To show the current stack without modifying it:
+```
+perc> show               # Show current stack state
+45
+```
+
+## Hyper Operators
+
+Hyper operators work on all values on the stack simultaneously:
+
+```bash
+perc calc 1 2 3 4 5 [+]    # Sum all: 1+2+3+4+5 = 15
+# → 15
+
+perc calc 2 3 4 [*]        # Multiply all: 2*3*4 = 24
+# → 24
+
+perc calc 10 3 2 [-]       # 10 - 3 - 2 = 5
+# → 5
+
+perc calc 100 5 2 [/]      # 100 / 5 / 2 = 10
+# → 10
+
+perc calc 2 3 2 [^]        # (2^3)^2 = 64
+# → 64
+
+perc calc 100 7 3 [%]      # 100 % 7 % 3 = 2
+# → 2
+```
 
 ## Building