Corion explained that it's proper for strict not to give an error, but Perl could certainly emit a warning or throw an error.

The only complication would be backwards compatibility. People rely on the behaviour of a conditionally executed my even though the docs have long warned against it.

sub foo {
   my $x if 0;
   print ++$x, "\n";
}

foo() for 1..3;
[download]

1
2
3
[download]

Note that using the hardcoded zero there warns Deprecated use of my() in false conditional.