for my $i ( 1..9 ) { print $i }
for my $i ( range(1,9) ) { print $i }
{ my $i; while ( range 1,9 => $i ) {...} }
{ my $iter = range(1,9); while ( $iter->(my $i) ) {...} }

##</code><code>##

sub range {
    my $start = shift;
    my $end = shift;
    if (!@_) {
        if (wantarray()) {
            return $start .. $end;
        } else {
            my $i = $start;
            return sub {
                return undef if $i > $end;
                $_[0] = $i++;
                return 1;
            };
        }
    }
    if (defined($_[0])) {
        ++$_[0];
    } else {
        $_[0] = $start;
    }
    if ($_[0] > $end) {
        return $_[0] = undef;
    } else {
        return 1;
    }
}