you need to use numeric comparison rather than string comparison. Aka. <=> or the "spacship operator". Change cmp to <=>. See perlop

Update In the intrest of being complete: You may have troubles if not all values are numeric. I believe that Regex::Common::Number can help you identify numbers as opposed to strings.

Update 2: I just checked.... numbers should sort lexicographically prior to letters... that should not cause much of an issue. Sorry for the false lead.