use YAPE::Regex::Explain; print YAPE::Regex::Explain->new( qr/address(.*)\d/ )->explain; __END__ The regular expression: (?-imsx:address(.*)\d) 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): ---------------------------------------------------------------------- address 'address' ---------------------------------------------------------------------- ( group and capture to \1: ---------------------------------------------------------------------- .* any character except \n (0 or more times (matching the most amount possible)) ---------------------------------------------------------------------- ) end of \1 ---------------------------------------------------------------------- \d digits (0-9) ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------