our $rgx_plain = qr/^([a-z]+)\d*$/;
  our $rgx_fancy = qr/
                       ^         # beginning of string
                       (         # begin cap $1
                         [a-z]+  #   one or more letters
                       )         # end cap $1
                       \d*       # optional digits
                       $         # end of string
                     /x;

##</code><code>##

  say $rgx_plain;
  say clean_regex($rgx_fancy);

##</code><code>##

  say clean_regex($rgx_plain);