First off, this should've been in the Scripts & Pop-ups Forum.
Secondly, I regret to say that I can't assist with this problem as I'm unable to find any reference to the $parms identifier, and I'm unable to locate a copy of mIRC 5.3 to check it's help file for what the $parms identifier returns.
I'd also recommend that you update to the most recent version, which is 6.17