To get you on the right track, super-simple example:

#!/usr/bin/perl
use threads;
use threads::shared;
use strict;

our $a:shared = 1;

print "main start->$a\n";

threads->create(\&display);
threads->create(\&display1);

print "hit enter to finish\n";
<STDIN>; #pauses for keypress
print "main done-> $a\n";

sub display {
   our $a = 2;
   $a++;
   print "from t1->$a\n";
}

sub display1 {
  our $a = 99;
   print "front2->$a\n";
   $a++;
lock $a;
cond_broadcast($a);
}
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