I have 6.16
Code:
on 1:text:-addblist *:#:{
  msg #Tes  triggered: $1-
}


and from another instance of mirc I used this alias for test input:
Code:
/addb {
  msg #Test This is a test alias
  msg #Test -addblist some_host
  msg #Test -addblist
  msg #Test -addblistshouldn't trigger
  msg #Test -addblist some_host multi word
  msg #Test shouldn't trigger -addblist blah
}

I got this result:
Quote:
<Bob> This is a test alias
<Bob> -addblist some_host
> triggered: -addblist some_host
<Bob> -addblist
<Bob> -addblistshouldn't trigger
<Bob> -addblist some_host multi word
> triggered: -addblist some_host multi word
<Bob> shouldn't trigger -addblist blah

Isn't that behaving the way you want it to?