#!/usr/bin/perl
use warnings;
use strict;
use experimental qw( signatures );

sub non_oxford_list($s) {
    $s =~ s/,([^,]+)$/ and$1/r
}

use Test::More tests => 3;

is non_oxford_list('A'), 'A';
is non_oxford_list('A, B'), 'A and B';
is non_oxford_list('A, B, C'), 'A, B and C';