You can even shorten the script further by placing those slap messages, including the $1 identifier line by line vertically, in a txt file called, say, 'slap.txt' and then play them to the targeted person on the channel.

alias slap { describe # $read(slap.txt) }

This way a random line from slap.txt will be played upon the trigger of slap alias. Of course, more messages can be added in the future.