use strict;
use warnings;

use 5.022;
use List::Util qw{ sum };

sub groupsOf (&$@);

say for groupsOf { sum @_ } 3, 1 .. 20;

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

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