http://www.perlmonks.org?node_id=980536


in reply to A simple grouping of list items

Just for fun, golfing... 
"" =~ /()/;
for (@list) {
  sleep(5) if !/^$1/;
  print;
  /^(.+)\:/;
}

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By the way the original script wasn't working if the items were ending with \n, because \n wasn't being replaced and $item was never matching $previous on the next iteration. However, if there were no \n characters, I had to set $| to non zero to get the expected behavior, otherwise output was getting buffered and was printed in one chunk at the very end.

In Section Cool Uses for Perl