$0

The identifier $0 is used in conjunction with $1. Technically it returns the number of tokens in the parameter passed. Unless the tokenize command has been used this defaults to being spaces for commands and commas in identifers, hence $0 will return the number of words in most cases.

Examples

When used in an alias it can look something like this.

alias count_words { echo -a That was $0 words }

Usage: /count_words Here is a sentence I want to count the words in..

When used in an event it acts the same.

on *:text:!count *:#mirc:{ msg $chan That was $0 words }

Usage: !count Here's another sentence we want to have fun with!

Note that $0 returns total number of tokens, meaning that in the event example above it will also count the word !count as being part of the sentence. You can bypass this by using $calc($0 - 1). This is not the case for the alias.