You can open sox with IPC, but the syntax can be tricky, see I need some help with open2 You need to get the | and - syntax right.
The syntax for sox can be tricky, so search google and groups.google for
"perl sox".
You need to read all the docs that come with sox and mpg123, to find the recommended syntax for interactive playing. To be honest, mplayer is probably easier to work with interactively. See Perl/Tk front-end to mplayer
As far as mpg123 goes, this should show a trick
#!/usr/bin/perl
use warnings;
use strict;
use Tk;
# read README.remote in mpg123 sources
# only works after mainwindow is closed ????
$|++;
my $pid = open(FH,"| mpg123 -@ - ");
print "$pid\n";
my $mw = new MainWindow;
my $startbut = $mw->Button(-text =>'Start Play',
-command => sub{
syswrite(FH, "1bb.mp3\n") ;
})->pack;
MainLoop;
|