Two questions.

1. Have you written that all at once or in small parts, verifying that each small chunk works. If all at once, don't be surprised it doesn't work, and especially don't exepct us to just read it all through and find all bugs. If in parts, can you give us hints in what part of the code you're sure works and what might not?

2. In

            print $sock "/JOIN $channel\r\n";
[download]

why the fuck are you sending that slash?

Update: 3. also, are you sure that input handler will not read more than one lines at once and treat them as a single line? Or what about partial lines? Also, use proper regexps so you don't pick up a random word snippet like QUIT somewhere inside a message. Try something like /^(?::\S+\s+)QUIT/ or something. Or better, parse the line to source, command, and argument list properly.