c:\@Work\Perl>perl -wMstrict -le "use YAPE::Regex::Explain; ;; print YAPE::Regex::Explain->new(qr/[need]+$/)->explain; " The regular expression: (?-imsx:[need]+$) matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?-imsx: group, but do not capture (case-sensitive) (with ^ and $ matching normally) (with . not matching \n) (matching whitespace and # normally): ---------------------------------------------------------------------- [need]+ any character of: 'n', 'e', 'e', 'd' (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- $ before an optional \n, and the end of the string ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------