I'm a little fuzzy on what you're asking, but it sounds like you want to match case-insensitively, or perhaps, convert from mixed-case to all one-case.

I think you might want to look at the /i regular expression modifier, explained in perlretut and perlre, or the uc and lc functions, explained in perlfunc.

You can change the capitalization in portions of strings with the \l and \u metacharacters (for one char at a time) or the \L, \U, and \E metacharacters (for altering the case of chunks of characters). These are also described in detail in perlretut.

Update: Thanks Anonymous Monk for finding a more accurate way to express my thought. I've corrected the verbage.