XML::Simple is probably the easiest place for you to start. Take a look at the ForceArray parameter to get a more consistent data structure. Once you have a data structure, dump it with Data::Dumper or the like to see what you're working with.

use XML::Simple;
use Data::Dumper;

my $xml = '<xml><item><key1>someValue</key1><key2>someValue</key2><key
+3>someValue</key3><key4>someValue</key4></item><item><key1>someValue<
+/key1><key2>someValue</key2><key3>someValue</key3><key4>someValue</ke
+y4></item></xml>';

my $data = XMLin($xml, ForceArray => 1);
print Dumper($data);
[download]