my $text = 'This is just an arbitrary example of text.';

#ONLY TWO WORDS ARE CAPTURED--WE WANT TO HIGHLIGHT ONLY THOSE
my $query = qr~(?:(?:This)|(?:That)).*?(just).*?(arbitrary).*?$~;

#THIS WOULD HIGHLIGHT THE ENTIRE LINE
$text =~ s~($query)~<span class="highlight">$1</span>~g;