Unless I've missed something obvious, this script doesn't seem to do anything. Essentially it creates and defines one lexical variable and one subroutine. The subroutine isn't called and the variable isn't used.

So either this isn't your entire script (in which case the line number in the warning is meaningless to us) or this isn't a script at all, but a module which you use somehow - but that would be odd given the hashbang line and the .pl extension.

Can you provide some more info about what this code is and how it is executed?