[user@host]$ perl -e 'print reverse sort{/(:\d+:))/<=>/(:\d+:/)}<>' /etc/passwd Unmatched ) in regex; marked by <-- HERE in m/(:\d+:)) <-- HERE / at -e line 1. [user@host]$ perl -e 'print reverse sort{/(:\d+:)/<=>/(:\d+:/)}<>' /etc/passwd Unmatched ( in regex; marked by <-- HERE in m/( <-- HERE :\d+:/ at -e line 1. [user@host]$ perl -e 'print reverse sort{/(:\d+:)/<=>/(:\d+:)/}<>' /etc/passwd