Put it on the queue? As data to create a new serialport object, not the serialport object itself?

So setup

sub Main {
    my $qin  = Thread::Queue->new();
    my $qout = Thread::Queue->new();

    my $guithread = threads->create( \&tkgui, $qin, $qout );

## don't wait for background downloading service / mechtitles
    threads->create( \&mechtitles, $qin, $qout );

    $guithread->join;    ## wait for gui to finish

    return;
} ## end sub Main
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Then from tkgui somewhere (a button), you tell "mechtitles" to create a newserialport with a message

my $message =  { newserialport  => [qw/ COM6 baudrate 11 ... /] } ;
$qin->push( $message );
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Then back in mechtitles, you have a dispatch table, and you use the message from $qin to invoke a callback to create a new serialport (and replace existing serialport)

sub mechtitles {
    my( $qin, $qout ) = @_;
    threads->detach();    ## can't join me :)


    my %dispatch = (
        newserialport => \&newserialport,
        pollserialport => \&pollserialport,
    );
    
    my %stash; ## STATE
    require Time::HiRes;

    while( 1 ) {
#~         if( defined( my $url = $qin->popnow ) ) {
        if( defined( my $action = $qin->pop ) ) {
            my( $callbackname, $callbackargs ) = %$action;
            if( my $callback = $dispatch{$callbackname} ){
                $callback->(\%stash, $qout, @$callbackargs );
            }
        }
        
        Time::HiRes::usleep( 33 * 1000 ); ## microseconds versus milis
+econds? grrdoh
    }
} ## end sub mechtitles

sub newserialport {
    my( $stash, $qout, @args ) = @_;
    my $serialport = Win32::SerialPort->new( ... @args ... );
    ...
    ### THERE IS A NEW STASH IN TOWN
    $stash->{serialport} = $serialport;
} ## end sub newserialport 

sub pollserialport {
    my( $stash, $qout, @args ) = @_;
    ...
    my $data = $stash->{serialport}->read(1); ## %stash!!!!
    ...
    $qout->push( { frobnicatetextdisplay => [ ... $data ... ] );
}
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