use strict;
my $str = '<!-- Text --><b>Text</b>
<a href="google.com">Link</a>
<div class="col"><h1>Nested Content</h1><p>More content</p>
</div>
<!-- END of Text -->';
my $regex = qr/<!--((?:(?!-->).)*)-->((?:(?!<!--)[\s\S])+)<!--((?:(?!-->).)*)-->/mip;
my $subst = '';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html