This is a server-based expoit, not a user-based exploit, so as long as you're connecting to a trusted IRC network, such as one of the major networks, you should be fine.
That said, I can't seem to reproduce this issue here so far, neither in a clean install of the release version nor in a debug version of mIRC.
When I test the perl script and make mIRC connect to the local perl server, nothing happens, other than a disconnect from the server because the server sequence is incorrect.
When I test the same string sequence using internal debugging in mIRC, again nothing happens other than mIRC opening a query window to that user.
I'll continue to try to reproduce this issue and if verified I should have an update out shortly.