#file: test.Mongo.pl
 use strict;
 use warnings;

 use MongoDB; # also loads MongoDB::MongoClient
 use Data::Dumper;

 my $connect_string=$ARGV[0];
 my $client = MongoDB::MongoClient->new({'host' => $connect_string});
 my $doc    = $client->get_database('mydb')->get_collection('mycoll')->find_one();
 $client->disconnect;
 print Dumper $doc;