Link Filters
Link filters are used to replace text such as 'Bug #42' with an automatic
link to some external resource. It uses regular expressions to replace the text.
Specify the search pattern in the pattern field without delimiters. Specify the entire
string you would like to use as a replacement with $x to insert the matched text. For example:
Pattern: "bug #(\d+)"
Replacement: "<a href=http://example.com/bug.php?id=$1>Bug #$1</a>"