#!perl -p0

s/<!-(-.*?-)->/ (my $x = $1) =~ tr,-,,s; $x = '--' if $x eq '-'; "<!-$
+x->" /gse;

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UPDATE: Fixed so it no longer turns <!----> into <!--->. Thanks to extremely for pointing that out.

UPDATE: Caveat: don't use this code on files where Perl code may be embedded in an HTML comment, as in this HTML::Mason example: <!-- <% $x-- %> -->. Thanks to extremely for pointing this out too.

In reply to fix bad HTML comments by chipmunk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


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