perl -wMstrict -E 'my $x=0; say $x||1; say $x//2;'
1
0

##</code><code>##

use warnings;
use strict;

this(arg => 0);

sub this {
    my %args = @_;
    do_something("if\n") if $args{arg};
    do_something("if def\n") if defined $args{arg};
}
sub do_something{
    print shift;
}