Because PHP has PHP regex, not Perl regex. This site is perlmonks, about Perl, not PHP. Go visit phpmonks.org :)

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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

In reply to Re^5: Reg expression to replace URLs with Anchor tags in Tweets by merlyn
in thread Reg expression to replace URLs with Anchor tags in Tweets by halfbaked

Title:
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