What I do is create the worker thread once during the startup of the script, and put the thread to sleep. Then when I want it to do something, I use threads:shared to turn it on and pass it a string to be used (a mp3 name).

If it is only mp3 files you want to play, you might be able to use a piped open to your mp3 player, and just feed it filenames on STDIN. I've done this in linux. (I realize you are on windows, but this just demonstrates the idea)

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

#read README.remote in mpg123 sources 

$|++;

#my $pid = open(FH,"| mpg123 -R  2>&1 "); 
my $pid = open(FH,"| mpg123 -R >/dev/null 2>&1 ");
print "$pid\n";

my $mw = new MainWindow;

my $startbut = $mw->Button(-text =>'Start Play',
          -command => sub{
           syswrite(FH, "LOAD 1bb.mp3\n") ;
          })->pack;


my $pausebut = $mw->Button(-text =>'Pause',
          -command => sub{
           syswrite(FH, "PAUSE\n") ;
          })->pack;

my $exitbut = $mw->Button(-text =>'Exit',
         -command => sub{ exit })->pack;

MainLoop;
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