c:\@Work\Perl\monks>perl -wMstrict -le
"use YAPE::Regex::Explain;
 ;;
 my $rx = qr{ [0-9] | [a-e]:[0-9] | [a-e] }xms;
 print YAPE::Regex::Explain->new($rx)->explain;
"
The regular expression:

(?msx-i: [0-9] | [a-e]:[0-9] | [a-e] )

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?msx-i:                 group, but do not capture (with ^ and $
                         matching start and end of line) (with .
                         matching \n) (disregarding whitespace and
                         comments) (case-sensitive):
----------------------------------------------------------------------
  [0-9]                    any character of: '0' to '9'
----------------------------------------------------------------------
 |                        OR
----------------------------------------------------------------------
  [a-e]                    any character of: 'a' to 'e'
----------------------------------------------------------------------
  :                        ':'
----------------------------------------------------------------------
  [0-9]                    any character of: '0' to '9'
----------------------------------------------------------------------
 |                        OR
----------------------------------------------------------------------
  [a-e]                    any character of: 'a' to 'e'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------