use strict;
use warnings;

use feature qw{ say };

sub groupsOf (&$@);

my %hash = map { $_ => int rand 50 } q{a} .. q{z};

say qq{$_\n-----}
   for groupsOf { join qq{\n}, map { qq{$_ => $hash{ $_ }} } @_ }
   10,
   sort { $hash{ $a } <=> $hash{ $b } } keys %hash;

sub groupsOf (&$@)
{
    my $rcToRun  = shift;
    my $groupsOf = shift;

    my $rcDoIt;
    $rcDoIt = sub
       {
           $rcToRun->(
              map shift, 1 .. ( @_ < $groupsOf ? @_ : $groupsOf )
              ),
           @_ ? &$rcDoIt : ();
       };

    &$rcDoIt;
}