When I run your script, an error about DBD::Proxy and the mysql driver info is never displayed. I believe the problem has something to do with this line, though I'm not sure what the actual problem is:

my @datasources = DBI->data_sources($driver);

If I remove the statements that deal with the data_sources, it works fine:

#!/usr/bin/perl

use strict;
use DBI;

my @drivers = DBI->available_drivers();

die "No drivers found!\n" unless @drivers;

foreach my $driver ( @drivers ) {
  print "Driver: $driver\n";
}
[download]

Which returns:

Driver: ADO
Driver: ExampleP
Driver: Oracle
Driver: Pg
Driver: Proxy
Driver: mysql
[download]

Maybe DBD::Proxy has a problem with data_sources?