open(F, ">foo.txt") or die "hey, couldn't open foo.txt";

##</code><code>##

if (!open(F, ">foo.txt")) {
   die "hey, couldn't open foo.txt";
}

##</code><code>##

# does not work
die "missing arg $_" unless $args{$_} for (qw(foo bar baz boop));

##</code><code>##

# untested
for (qw(foo bar baz boop)) {
  die "missing arg $_" unless $args{$_};
}