A more recent version of scripts may be available at scripts.irssi.org.
This script is no longer maintained.
please use trigger.pl, it has all the features of replace.pl and much more.
I've written a script to convert your old replaces file to a triggers file: convert-replace-trigger.pl
This is not an irssi script. You should use this from the command line.
perl convert-replace-trigger.pl [irssi-dir]
if no directory is specified, it will asume you use the default ~/.irssi
You can still download the old script.