sure, first %x is set with value plaintext

$eval(%x,2)then we try to evaluate %x twice with //noop $eval(%x,2)

1. %x evaluates once to produce its value, the string

$eval(%x,2)2. this result is evaluated again, so mirc attempts to evaluate $eval(%x,2) once which takes us back to step 1

this process happens over and over again, and internally the stack keeps getting added to over and over to nothing is ever removed from it. eventually it throws that error :P

you can see just how far it reaches by using the following:

alias stackoverflow inc -su %x | return $!eval($stackoverflow,2)

then try //noop $eval($stackoverflow,2)