He [the art teacher] was not that much older than I was
He had taken our class to the Metropolitan Museum
He asked us what our favorite work of art was,
But never could I tell it was him
Oh, I wish I could tell him --
Oh, I wish I could have told him
(Rufus Wainwright; The Art Teacher (a song))
Does 'I wish I could tell him' have some specific purpose here (maybe it suggests that there is still a possibility of telling him?), because, in my humble opinion, the author surely means 'I wish I could have told him'?
(I'm fully aware that songs can't be always a reliable source of the English language)
'I wish I could tell him' - you might still get the chance to tell him.
'I wish I could have told him' - it's too late; you'll never get the chance now.