sub warns (&) {
	my $sub = shift;
	my @warns;
	{ local $SIG{__WARN__} = sub { push @warns, shift }; $sub->() }
	return wantarray ? @warns : scalar @warns;
}

print "<$_>\n" for warns { warn "Hello"; warn "World" }

__END__
<Hello at - line 8.
>
<World at - line 8.
>