>perl -wMstrict -le
"my $s = 'aaxbbbxccccxddxex';
 ;;
 printf qq{'$_' } for $s =~ m{ [a-e]+ x }xmsg;  print '';
 ;;
 printf qq{'$_' }
   for $s =~ m{ [bd]+ (*SKIP)(*FAIL) | [a-e]+ x }xmsg;  print '';
 ;;
 printf qq{'$_' }
   for $s =~ m{ (?: [bd]+ (*SKIP)(*FAIL))? [a-e]+ x }xmsg;  print '';
"
'aax' 'bbbx' 'ccccx' 'ddx' 'ex'
'aax' 'ccccx' 'ex'
'aax' 'ccccx' 'ex'