use strict;
use warnings;
use Data::Dump::Streamer;

my $value = undef;

print !!$value;

my $nothing = nothing ();
my $retNothing = retNothing ();
my $retUndef = retUndef ();
my $retFalse = retFalse ();
my $retFalse2 = -retFalse ();

Dump (\$nothing);
Dump (\$retNothing);
Dump (\$retUndef);
Dump (\$retFalse);
Dump (\$retFalse2);


sub nothing {
}

sub retNothing {
    return;
}

sub retUndef {
    return undef;
}

sub retFalse {
    return 1 == 0;
}