use warnings;
no warnings "uninitialized";
use strict;
use WWW::Mechanize;

use MIME::Types;
my $mt = MIME::Types->new;

my $mech = WWW::Mechanize->new();
$mech->get("http://dspace.mit.edu/handle/1721.1/53720");

for my $link ( $mech->links() )
{
    my $uri = $link->url_abs();
    print $uri, $/
        if $mt->mimeTypeOf($uri->path) eq "application/pdf";
}

# http://dspace.mit.edu/bitstream/handle/1721.1/53720/MIT-CSAIL-TR-2010-018.pdf?sequence=1