You'll note that the original subject was 'Tail call optimization' not 'Tail recursion optimization'. Tail call optimization comes in handy even when you're not recursing. It comes in handy when you're using lots of simple methods that simply return the results of a simple function call

package LeafNode;
...
sub accept {
    my($self, $visitor) = @_;
    $visitor->visit_leaf($self);
}
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When you have tail call optimization in place, visit_leaf can return directly to accept's caller('s caller's caller's ...). Even without recursion, this can be a win because stack frames can be costly to create.