use strict;
use warnings;

sub gen_range_step {
    my ( $start,$stop,$step ) = @_ ;

    my $current = $start;

    return sub {
        my $val   = $current;
        $current += $step;
        return $val if $val <=$stop;
        return;
    }
}

my $iter = gen_range_step(5,20,4);

while ( my ($val) = $iter->() ) {
    print "$val\n";
}

##</code><code>##

    
C:/Strawberry/perl/bin\perl.exe -w d:/tmp/pm/generator_iterator.pl 
5
9
13
17

Compilation finished at Sat Nov 13 21:18:20