You can use this method and check a saved list of nicknames.
%var = nick1,nick2,nick3
if ($istok(%var,$nick,44))
$hget(table,nicks) = nick1,nick2,nick3
if ($istok($hget(table,nicks),$nick,44))
You can also use isin which is faster but not as accurate.
if ($nick isin %var)
$nick = tru
But a nickname stored, Truth, would return $true but not be accurate.