You have a token: ":ATMA!~fixed@Matrixn3t.net PART #future".
It's ASCII number ($asc(!)) is 33. You need the 1st part the string separated by chars like it.
So, you'd have it using $gettok(:ATMA!~fixed@Matrixn3t.net PART #future, 1, 33), which returns ":ATMA".
To get rid of that ":", you can use either $remove(:ATMA,:) or $mid(:ATMA,2).
Concluding the method, you'd have $mid($gettok(:ATMA!~fixed@Matrixn3t.net PART #future,1,33),2).
Now, supposing your variable is %var, you'd use $mid($gettok(%var,1,33),2).
Or if you want it to be an alias, you'd use..
alias _nick { return $mid($gettok($1,1,33),2) }
..Then you'd use $_nick(<your line here>) everywhere.
Such a colourful-detailed reply.. I need sleep..