use YAPE::Regex::Explain; print YAPE::Regex::Explain->new(q<^(.*)\/([^\/]*)>)->explain(); __output__ The regular expression: (?-imsx:^(.*)\/([^\/]*)) 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): ---------------------------------------------------------------------- ^ the beginning of the string ---------------------------------------------------------------------- ( group and capture to \1: ---------------------------------------------------------------------- .* any character except \n (0 or more times (matching the most amount possible)) ---------------------------------------------------------------------- ) end of \1 ---------------------------------------------------------------------- \/ '/' ---------------------------------------------------------------------- ( group and capture to \2: ---------------------------------------------------------------------- [^\/]* any character except: '\/' (0 or more times (matching the most amount possible)) ---------------------------------------------------------------------- ) end of \2 ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------