I confused "scope" with "stack frame". While if creates a lexical scope, no stack frame is created.

Because if creates a lexical scope, the following dies:

>perl -e "use strict; if (my $x = foo()) { } print $x;
Global symbol "$x" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.
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If if created a stack frame, the following would print abcde instead of abced:

sub P1::DESTROY { print 'd'; }
sub P2::DESTROY { print 'c'; }
{
   print('a');
   if (my $x = bless({}, 'P1')) {
      my $y = bless({}, 'P2');
      print('b');
   }
   print('e');
}
print("\n");
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Anyway, I didn't find an answer to your question.