There isn't one as far as I know, though you might be able to find a script that solves it.
The problem is that many IRC servers cut off lines after a maximum of 512 bytes, including commands and data that aren't visible to the users. As far as I know, mIRC instead emits a beep to alert the user that they're over the limit.
So, when someone pastes multiple lines, they often get cut off by the server without them being aware of it. It can be a bit of a pro
