@ mIRCManiac: Hitting "Cancel" should only halt the command in which "$$?" is used.
I can't use $, I MUST use $$.
I try to explain it better with another example:

alias firstrun {
nick $$?="Please insert your nick"
anick $$?="Please insert your alternative nickname"
}

In this case, the user must have the possibility to set/change alternative nick, without setting/changing the main nick.
In 6.17 if you press Cancel at the first request, the entire alias is stopped, so the input request for alternative nick will never come.

In mirc 6.16 it works good, so I suppose it's a bug of v6.17.