#!/usr/bin/perl -w
use strict;

my $str = '<P_contrib-author>Mariel Miller</P_contrib-author>,<P_contrib-author>Allyson Fiona Hadwin</P_contrib-author>,<P_contrib-author>Jenna Cambria</P_contrib-author>';

my @authors = 
   ($str =~ /<P_contrib-author>\s*(.*?)\s*<\/P_contrib-author>/g); 
   
if (@authors >= 3)
{
   print join (", ", @authors[0..@authors-2]), 
         " and $authors[@authors-1]\n";
}
elsif (@authors == 2)
{
   print "$authors[0] and $authors[1]\n";
}
else
{
   print "$authors[0]\n";
}