Since the loop stop when undefined is returned, the following is the same, but simpler:

sub reverse_iterator {
    my @list = @_;
    sub {
        return pop @list;
    };
}
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Update: I prefer to signal the end of the list out of band to allow undefined values in @list. That why I prefer returning the value through an argument.

sub reverse_iterator {
    my @list = @_;
    sub {
        return unless @list;
        $_[0] = pop @list;
        return 1;
    };
}

my $foo = reverse_iterator(@ARGV);
while ($foo->(my $val)) {
    print("$val\n");
}
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Update: I just noticed that you assigned to $_ without localizing it first. Don't do that!

Update: s/shift/pop/

So how about this as an alternative?:

#!/usr/bin/perl -l

sub revlist {
  my @list = @_;
  sub { pop @list };
}

my $foo = revlist(@ARGV);

print while local $_ = $foo->();
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Edit: Optionally, closure subroutine might look like this, of course:

sub { return unless @list; pop @list; };

print substr("Just another Perl hacker", 0, -2);

- apotheon CopyWrite Chad Perrin

my $foo = reverse_iterator("a",undef,"c");
while (my ($elem) = $foo->()) {
   print( defined( $elem ) ? $elem : "undef" );
}
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