use strict;
use warnings;
use XML::XPath;

my $xp  = XML::XPath->new(filename => 'mdlist.xml');
my @mds = map { 
   $_->getAttribute('name') 
} $xp->findnodes('/md_map/md[@name]');


for my $dir (@mds) {
   # create $dir if applicable
}	

##</code><code>##

my $callout_loc = '/path/to/xml/stuff';
my $file        = "$callout_loc/mdlist.xml";

##</code><code>##

mkdir $dir or warn "$dir already exists: $!";