@list = ( 'a' .. 'z' );

##</code><code>##

a b c d e, # arr[0]
f g h i j, # arr[1]
k l m n o, # arr[2]
p q r s t, # arr[3]
u v w x y, # arr[4]
z          # arr[5]

##</code><code>##

#!usr/bin/perl

use strict;
use warnings;

my @list = ( 'a' .. 'z' );
my $string_chunk5 = _string_chunk5( @list );
my @array_chunk5 = _array_chunk5( @list );
print "String chunk of 5 =\n$string_chunk5\n";
print "Array chunk of 5 =\n@array_chunk5\n";

sub _string_chunk5 {
    my @arr = @_; 
    return join( " ", @arr ) unless @arr > 5;
    return join( " ", splice( @arr, 0, 5 ) ). ",\n" . _string_chunk5( @arr );  
}

sub _array_chunk5 {
    my @arr = @_; 
    # Base case == when @arr is <= 5
    return ( join( " ",  @arr ) ) unless @arr > 5;
    # what goes here ?
}