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

my %shash;
#share(%shash); #will work only for first level keys 
my %hash;

 share ($shash{'go'});
 share ($shash{'fileno'});
 share ($shash{'pid'});
 share ($shash{'die'});

 $shash{'go'} = 0;
 $shash{'fileno'} = -1;
 $shash{'pid'} = -1;
 $shash{'die'} = 0;

 $hash{'thread'} = threads->new(\&work);

 $shash{'go'} = 1;

sleep 1;  # cheap hack to allow thread to setup 

my $fileno = $shash{'fileno'};
open (my $fh, "<&=$fileno") or warn "$!\n";

while ( <$fh> ){ print "In main-> $_";  }

#wait for keypress to keep main thread alive 
<>;

# control-c to exit

################################################################## 
sub work{
    $|++;
    while(1){
       if($shash{'die'} == 1){ goto END };

       if ( $shash{'go'} == 1 ){

        my $pid = open(FH, "top -b |" ) or warn "$!\n";
        my $fileno = fileno(FH);
        print "fileno->$fileno\n";
        $shash{'fileno'} = $fileno;

    $shash{'go'} = 0; #turn off self before returning       
       }else
         { sleep 1 }
    }
END:
}
#####################################################################