The on CTCPREPLY event triggers when a user sends a standard ctcp reply to a ctcp that you initiated.
Format: on <level>:CTCPREPLY:<matchtext>:<commands>
Example: on 1:CTCPREPLY:VERSION*:/echo $nick is using IRC client: $1-
For an explanation of matchtext see the on TEXT event.
on 1:CTCPREPLY:PING*:/echo $nick replied to my ping!
This triggers when a user replies to a ctcp PING that you sent.