URLs like the one in your example can be matched with a regular expression like
($url) = /href=\"([^\"]+)\"/i
If the HTML ever uses single quotes (or no quotes) around a URL, or if there are ever quote characters in the URL, then this will not work quite right. For this reason, you will get some answers telling you not to use regular expressions to parse HTML. Heed them but carry on if you are confident that the input will be well behaved.
