c:\@Work\Perl\monks>perl -wMstrict -le "use YAPE::Regex::Explain; ;; print YAPE::Regex::Explain->new('^(.+)(e|r)(.*)$')->explain; " The regular expression: (?-imsx:^(.+)(e|r)(.*)$) 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 (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- ) end of \1 ---------------------------------------------------------------------- ( group and capture to \2: ---------------------------------------------------------------------- e 'e' ---------------------------------------------------------------------- | OR ---------------------------------------------------------------------- r 'r' ---------------------------------------------------------------------- ) end of \2 ---------------------------------------------------------------------- ( group and capture to \3: ---------------------------------------------------------------------- .* any character except \n (0 or more times (matching the most amount possible)) ---------------------------------------------------------------------- ) end of \3 ---------------------------------------------------------------------- $ before an optional \n, and the end of the string ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------