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The other missing feature is that it treats all repeated characters like underlines
The Perl program didn't
          I am a heading
          **************
          I am NOT a heading
          **************
          I am not a heading either
          ************************************
Perl handled this:
          if (/^(.)\1+$/ && defined($held) && length($_) == length($held)) {
sed has no (easy) way to compare the lengths of two strings
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