use strict;
my $str = 'única<div data-sort="1">
<p>dolor</p>
<p>única</p>
<h1 data-position="1" eiusmod="foo" >Lorem ipsum dolor sit amet</h1>
<div data="eiusmod"></div>
<strong>search here : consectetur adipiscing elit, </strong>
<div>
sed do <u>eiusmod</u> tempor <mark>incididunt</mark> ut dolor et dolor dolor magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</div>
Duis aute irure <i>dolor</i> dolor in dolor dolor reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
</div>
<div>
sed do <u>eiusmod</u> tempor <mark>incididunt</mark> ut única et única púnica magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</div>
<div>fetén</div>
';
my $regex = qr/((?:<[^>]*>[^<]*?)*?(?:(?!<mark>)<[^>]*(?=>))?)(\W|^)(eiusmod|sort|incididunt|dolor|única|feté)(?=\W|$)/mup;
my $subst = '\\1\\2<mark>\\3</mark>';
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