Not allowed? 
$ perl5.15.9 -wE 'my $x = 1 if 2; say $x // "???"'
1
$ perl5.15.9 -wE 'my $x = 1 if 0; say $x // "???"'
???
$

[download]
I won't recommend it, but it is still allowed. I thought it started warning under certain conditions since 5.14, but I'm not able to reproduce it.

In reply to Re^2: order of operations with conditionals at the end by JavaFan
in thread order of operations with conditionals at the end by BeneSphinx

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