Joe Drago's LOLCode Interpreter:

(uses Parse::RecDescent)

Available here:

http://drago.cc/lol/

It currently handles these constructs:

    * HAI - Beginning of program
    * KTHXBYE - End of program
    * IM IN YR [loop label] / KTHX - Loop construct
    * GTFO - "break" (out of a loop)
    * IZ [conditional]? [statement] - If statement (shorthand)
    * IZ [conditional] O RLY? \n YA RLY [statements] \n NO WAI [statements] KTHX - If statement (long version)
    * I HAS A [variable name] - Variable declaration
    * I HAS A [variable name] ITZ [value] - Variable declaration with initialization
    * BTW [text] - Comment
    * VISIBLE [identifier] ( N [identifier] ...) - Output text
    * BIGGER THAN / SMALLER THAN - Conditionals (for IZ)
    * UP [variablename]!![optional number] - Increment variable