Update: I went off on a different problem. This is more to the point.

To batch through an array I'd collect indexes so there is no doubt but that I am dealing with the actual elements in the loop body.

Like:

my $i;
my @ar = 0 .. 10;

($get_idx_grp, $fin_idx_grp) = mk_idx_funcs( 4, \$i, \@ar );

for ( $i = 0; $i < @ar; ++$i) {
    my @idx = &$get_idx_grp;
    $ar[ $idx[0] ] = "YYY";
    &$fin_idx_grp;
}

sub mk_idx_funcs {                       # XXX bad name
    my ( $grp_size, $iter, $array ) = @_;
    my ( @group, $group_end );
    my $first_call = 1;

    return ( sub {
            if ($first_call) {
                $first_call = 0;
                $group_end  = $$iter + $grp_size;
            }
            if ( $$iter < $group_end and $$iter < @$array ) {
                push @group, $$iter;
                no warnings;
                next unless @group==$grp_size or $$iter==@$array-1;
            }
            return @group;
        },
        sub {
            $group_end += @group;
            @group = ();
            return;
        }
    );
}
[download]

Original post follows

I would be interested in the aliasing most likely to avoid changing the identifiers in a loop body. Your code does not do this, so I do not understand what you are trying to achieve.

This seems simpler:

#!/usr/bin/perl
use strict;
use warnings;

my @array = 0 .. 30;

my $interval = make_interval();
for my $val ( @array ) {
    &$interval( 4);
    $val = "--";
};

local $, = " ";
print @array, $/;

sub make_interval {
    my $ctr = 0;
    my $start = 1;
    return sub {
        if ( $start) { $start = 0; return }
        $ctr++;
        if ( $ctr == $_[0]) { $ctr = 0 } else { no warnings; next }
    }
}
[download]