Smalltalk uses method dispatch and closures for control flow, which resembles the "Church encoding" in lambda calculus:

    3 < 4 ifTrue: [ 'true' ] ifFalse: [ 'false' ]

But very arguably that is still if-then-else, it's just not a special construct in the language. Avoiding Boolean values is also sometimes better to convey intent more precisely ("Boolean blindness"), but that's just a stylistic thing and not forbidding Boolean values entirely.