$ perl -w
sub nothing { return; }
sub something { return 0 == 1; }
my @foo;
push @foo, nothing();
print "foo has " . @foo . " elements after pushing nothing.\n";
push @foo, something();
print "foo has " . @foo . " element after pushing something.\n";
__END__
foo has 0 elements after pushing nothing.
foo has 1 element after pushing something.