It'll ignore everything it doesn't match. You don't have to do anything.

If $query contains a literal text to match: 

$str =~ s/\Q$query\E/<em>$query<\/em>/ig;

[download]

If $query contains a regex pattern: 

$str =~ s/($query)/<em>$1<\/em>/ig;

[download]

In reply to Re^5: How to use \W in Regular Expression? by ikegami
in thread How to use \W in Regular Expression? by Sachin

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