In the IO::Socket.pm that I can look into, the code is like

sub connect {
    @_ == 2 or croak 'usage: $sock->connect(NAME)';
    my $sock = shift;
    my $addr = shift;
    my $timeout = ${*$sock}{'io_socket_timeout'};
    my $err;
    my $blocking;

    $blocking = $sock->blocking(0) if $timeout;
    if (!connect($sock, $addr)) {
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so the call to connect should still be traceable a bit by single-stepping...Might help to know if the issue is before or after getting a local socket to use. Not that I think that would help too much, but it still might get you a bit closer to a solution.

Any chance to try the code on another machine ? Are you running this with the same privileges as when you do successfully telnet ? Maybe you can check if it behaves the same way when you run it as Administrator?