You're welcome, I'm actually going to use this code to keep improving the regex pattern so that it matches what mIRC is doing correctly.
Here is another update of the code:
on $*:hotlink:$($url_p):*:if ($hotlink(match).type == url) && ($hotlink(event) == dclick) { run firefox $regml(2) | return } | halt
alias url_p return m@(["']?)((?:(?:https?|ircs?)://(?:www\.)?|www\.)((?:(?:[-\w]+\.)+)[-\w]+)(?::\d+)?(/(?:[^ ]*))?)\1@igS
