Look for perldoc -q regex and perldoc -f quotemeta. I think that it's the proper way to do it. I don't know why converting to lower case via lc() also works.
--Artist
Comment on Re: Regular expression match trouble with "+"
It's the use of eq instead of m// that makes it work, not the conversion to lowercase. Converting to lowercase is to string compares what /i is to regexps.