#!/usr/bin/perl -l

use strict;
use warnings;
use Data::Dumper;
use XML::Simple;

my $bla = XMLin("primary.xml",
    ForceArray => [ qw(package) ],
    KeyAttr => [ ],
);

foreach my $i (0 .. $#{$bla->{package}}) {
    # The combination of fields name, epoch, 
    #   version, release and arch are (unique).
    $bla->{temp}{sprintf("%s-%s-%s-%s-%s",
            $bla->{package}[$i]{name},
            $bla->{package}[$i]{version}{ver},
            $bla->{package}[$i]{version}{rel},
            $bla->{package}[$i]{version}{epoch},
            $bla->{package}[$i]{arch},
        )} = $bla->{package}[$i];
}

($bla->{package}, $bla->{temp}) 
    = ($bla->{temp}, $bla->{package});
delete($bla->{temp});

print Data::Dumper->Dump( [\$bla], [qw(*bla)]);