$if function help please

I can't get this to work either!

I'm trying to format %title%. If the contents of tag %www% match 100% exactly tag %artist% I want to leave %title% as it is. If not, I want to append the contents of %www% to the end of %title%.

My action...
Format value
Field: title
Format string: $if(%www%=%artist%,%title%,%title% '['Feat. %www%']')

...which by my reading of the helpfile should be right, but if I replace %title%,%title% '['Feat. %www%']') from the above action with true, false) the %title% for all tracks, irrespective of values in %www% or %artist% ends up as true, so it looks like it's not matching exactly.

How do I tell it to match exactly?

Not tested.
Format string: $if($eql(%www%,%artist%),%title%,%title% '['Feat. %www%']')

Ah, bless ya. That's fixed it! Thanks!