Here's some skeleton code to try. I haven't tested it much, but it seems to connect alright.

#! /usr/bin/perl

use strict;
use warnings;

use Socket;
use POSIX;

sub named_socket_spawn {
    my $code = shift;
    ref $code eq 'CODE' or return;

    my ($serv, $conn);
    socket($serv, AF_UNIX, SOCK_STREAM, PF_UNSPEC)
                                        || die "socket: $!";

    my $sname = tmpnam();
    bind($serv, sockaddr_un($sname))    || die "bind: $!";
    listen($serv, 1)                    || die "listen: $!";

    my $pid = fork()                    // die "fork: $!";

    if ($pid) {
        close $serv;
        return $sname;
    }
    accept($conn, $serv)                || warn "accept: $!";
    unlink($sname)                      || warn "unlink: $!";
    open STDIN, "<&", $conn;
    open STDOUT, ">&", $conn;
    close $serv;
    close $conn;
    exit $code->();
}

use DBD::mysql;

#my $sqlsock = named_socket_spawn(sub{exec "ssh host -W host:3306"});
my $sqlsock = named_socket_spawn(sub{ exec "nc localhost 3306" });

my $dsn = "DBI:mysql:database=test;mysql_socket=$sqlsock";

my $dbh = DBI->connect($dsn, "test", "hunter5");
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Hm. According to DBD::mysql, there's the mysql_socket specifier to pass the unix socket name. Does this not work?

So basically, you'd need a small helper sub to handle the tedium of attaching a process to a socket

my $unixname = named_sock_spawn(sub{ exec "ssh" });

sub named_sock_spawn {
    socket();bind();listen();
    fork() and return $name;
    accept();dup();dup();$fun->();
}
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The perlipc has an example on unix-domain TCP. But are there any modules to provide named pipe utilities?

This is only for a socket name unfortunately, not for an in-memory socket structure.

It's the socket name that the mysql client will use to connect to the server. No?