this line: if ($key =~ /^(.*)(\d+)$/) should be if ($key =~ /^(.*?)(\d+)$/)

The reason you need the '?' there is that perl regexes are greedy. In your code (.*) consumes every character in $key and then fails to match any digits for the second group, (\d+). Then the regular expression engine will back up 1 character to try to make the match succeed. And it will, capturing the last char which is a digit. But what if your digits are more than 1 char? Your code would fail to capture all the digits since the regex was satisfied with only one of them.

The question mark makes the regex look to see if the next char is a digit, and if so, start capturing in the second group.

Chris