For the (imagined) central problem of sending an asynchronous message from outside the Perl process to the running Perl program, I think this emulation is sufficient. This at least brings the possibility to have some form of asynchronous communication between two Perl processes on Windows in a similar fashion as Unix.

Also, I imagine a fun application of SA_SIGINFO could be a hook like this:

$SIG{SIGINFO} = sub {
    my ($info) = @_;
    eval $info;
};
[download]

which basically gives you a detachable console to any Perl process.