This code:

sub foo {
    my $x if @_;
    return if @_;

    $x = 17;
    print $x, "\n";
    print sub { $x }->(), "\n";
    return;

}
foo(1); # make $x stale in all perl versions
foo;

produces errors and wrong output because it stales the $x:

17
Variable "$x" is not available at ./lexical_sub line 11.
Use of uninitialized value in print at ./lexical_sub line 11.


All perls since 5.10.1 are affected.

All Fedoras are affected.

Fixed in upstream by commit:

commit cae5dbbe30ba4a96ff5e570be0d90779f06fee71
Author: Father Chrysostomos <sprout>
Date:   Sat Aug 4 14:42:47 2012 -0700

    Close over stale vars in active subs