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

my @list = (
    [qw(a)],
    [qw(a b)],
    [qw(a b c)],
);

for (@list){
    print join_english(@$_), $/;

}

sub join_english {
    return $_[0] if @_ < 2;
    my $last = pop @_;
    return join(', ', @_), ' and ' . $last;
}