use strict ;
use warnings ;
use IPC::Open3 qw( open3 ) ;
use MCE::Loop ;

MCE::Loop::init {
   max_workers => 3, chunk_size => 10
} ;

my $cmd = 'perl readfiles.pl' ;

sub do_work {
	my @ar = @{$_[0]} ;
	my $id = $_[1] ;
	open( my $fho, ">", "output\\$id.txt" ) or die "Can't open > output\\$id.txt: $!" ;
	foreach ( @ar ) {
		print $fho $_ ;
	}
	close($fho) ;
}

my $pid = open3(
	undef,
	my $filedata,
	undef,
	$cmd, @_,
) ;
print STDERR "Starting MCE loop\n" ;
mce_loop_f {
   my ( undef, $chunk_ref, $chunk_id ) = @_ ;
   do_work( $chunk_ref, $chunk_id ) ;
} $filedata ;
print STDERR "Ended\n" ;

waitpid( $pid, 0 ) ;
warn "Failed\n" if ( $? << 8 != 0 ) ;
close($filedata) ;

##</code><code>##

use strict ;
use warnings ;

my @files = qw( data1.txt data2.txt data3.txt ) ;
foreach ( @files ) {
	open( my $fh, "<", $_ ) or die "Can't open < $_: $!" ;
	while(<$fh>) {
		chomp;
		print $_ . "\n" ;
	}
	close( $fh ) ;
}

##</code><code>##

use strict ;
use warnings ;

open( my $fh, ">", "data1.txt" ) or die "Can't open > data1.txt: $!" ;
for my $i ( 1..1000 ) {
	print $fh "$i\n" ;
}
close $fh ;

open( $fh, ">", "data2.txt" ) or die "Can't open > data2.txt: $!" ;
for my $i ( 1001..2000 ) {
	print $fh "$i\n" ;
}
close $fh ;

open( $fh, ">", "data3.txt" ) or die "Can't open > data3.txt: $!" ;
for my $i ( 2001..3000 ) {
	print $fh "$i\n" ;
}
close $fh ;