Snippet does work, aslong as you set a variable for %staffchan.
A basic blacklist script, using the syntax:

[!@]blist add/del/check/reason #channel (reason)

And it also will part the channel if it is on it when the blist is added.

on $*:text:/^[!@]blist/Si:%staffchan: {
  set %out $iif($left($1,1) == @, msg $cha, notice $nick) {
   if ($2 == add) {
   set %blist [ $+ [ $3 ] ] true
   set %blistr [ $+ [ $3 ] ] $4- {
     if ($me !ison $3) { halt }
     elseif ($me ison $3) { msg $3 This Channel Has Been Blacklisted. | part $3 } }
    }
    elseif ($2 == del) {
   if (%blist [ $+ [ $3 ] ] == $null) { 
      %out This channel is not currently blacklisted. }
    elseif (%blist [ $+ [ $3 ] ] == true) {
      unset %blist [ $+ [ $3 ] ]
      %out You have Unblacklisted the channel: $3 $+ . }
     }
   elseif ($2 == check) {
    if (%blist [ $+ [ $3 ] ] == $null) { %out $3 is not currently blacklisted. }
    elseif (%blist [ $+ [ $3 ] ] == true) { %out $3 is currently blacklisted. }
  }
    elseif ($2 == reason) {
    if (%blist [ $+ [ $3 ] ] == $null) { %out this channel is not Blacklisted. | halt }
    if (%blist [ $+ [ $chan ] ] == true) {
       if (%blistr [ $+ [ $3 ] ] == $null) {
      %out Reason for the blacklist of $3 $+ : N/A 
         }
      elseif (%blistr [ $+ [ $3 ] ] != $null) {
     %out Reason for the blacklist of $3 $+ : %blistr [ $+ [ $3 ] ] }
     }
    }
   else {
    %out you specified an Invalid parameter.
    %out $2 must be either: add, delete, check or reason. | halt
  }
 }
}
on *:invite:#: { join $chan {
     if (%blist [ $+ [ $chan ] ] == $null) { halt }
    else{
      msg $chan This channel is blacklisted. | part $chan }
   }
}