Demonstrate the leak in DBD::mysql that I noticed. If you fail to connect (down host), the program will leak memory. If you're connecting to a server that's up, there is no leak.

bdb_mysq_leak.pl

#!/usr/bin/perl -w
use strict;
use warnings;
use feature qw(say);
use DBD::mysql;

my $host = 'dev4h';
my $port = 9307;
my $dsn  = "DBI:mysql:host=$host;port=$port";
my $user = 'foo';
my $pass = 'bar';

while (1) {
    my $dbh = DBI->connect($dsn, $user, $pass);
    if ($dbh) {
        say "connected to $host:$port";
    } else {
        say "connect fail to $host:$port: $@";
    }
}

exit;
__END__