Even if there is any module preseent, can't you simply write subroutine with few lines of code? I don't think I need to post this code, I think monk of your level can easily do it.
in reply to Percentage module in Math::?
Please let us know why you want readymade module? From my experience of team managements and collaborative development environments, I know manytimes you need to restrict programmers to use standard modules to maintain consistancy and reliability of giant programs, If that is the case then I think here you can create your own library sub and distribute to your group.