lots of good answers--just want to tack on one note since OP said he's a regex first-timer.. These are all equivalent -- the /i on the end makes it case insensitive.. check the perlre man page for other modifiers (/m, /s, /x, and /g for substitutions).

m/[a-zA-Z]/
m/[a-z]/i
m/[A-Z]/i
[download]