A more recent version of scripts may be available at scripts.irssi.org.
With this script, you can use your mouse to control irssi: scroll with your scroll wheel, and execute command with mouse clicks or gestures.
It's based on mirage's irssi mouse patches: it's basicly irssi_mouse_xterm-0.6.patch translated to Perl, and more features added.
Clicking in your act bar (which you can do with the patch) isn't supported with this script (yet?)
You can still copy-paste using your mouse by holding down the shift button, or (by default) by clicking first to temporarily disable the script
If after unloading the script your terminal doesn't react to your mouse as it should, do this to reset your terminal to the default behaviour:
/script exec print STDERR "\e[?1000l";
1.0.0 (since 0.0.0)