Order of items in an array

[Rabbit Stoddard]

Question for Harlowe folks! 

I have an array that adds values as the user moves through passages. The order in which they visit the passages is important. So I want to compare two indexes of values in an array using an if statement, something like this: 

(if: $myvar.indexOf("room 1") < $myvar.indexOf("room 2")[things look bright!](else:)[you are eaten by a grue]

however, either .indexOf doesn't work, or it doesn't work like that, or there is something that I am missing, or I need to write a macro, at which point I'm not entirely sure where to begin. Any thoughts/assistance on this would be most appreciated. Thanks!