The expression used to to provide a list of possible values for a verb argument may reference the value of arguments prior to the one being expanded. It may even reference the value of the argument being expanded, but this will always be a text string equal to what the user has typed so far.
In addition, there is a special variable called “expanding” which is only accessible in this context. It is 1 if the user’s input is being expanded and 0 if the user’s final input is being validated. In certain rare cases, you may wish to tell the difference between these two cases. For example, you could use this to have possible values which do not show up in the expansion lists, but which are accepted when typed in full.
mob/verb/test(A in MyProc(A,expanding))
usr << "You typed: [A]"
proc/MyProc(A,expanding)
var/values[] = list("one","two","three")
if(!expanding) values += "secret"
return values