Code:
alias crash {
  goto $null
  :
}
alias crash2 { goto | : }

alias nocrash {
  var %i = -2
  :
  inc %i
  if (%i) {
    goto $null
  }
}

Simple: /crash or /crash2 will crash mIRC (v6.14), /nocrash will just give a * /goto: insufficient parameters

I've been doing some fancy scripting using the poor man's switch statement, this looks like the step too far grin