#! perl -sw
use strict;
use threads;
use threads::shared;
use Thread::Queue;
#  grep -h %search_string% *.txt > retuned_Results.sl

our $THREADS //= 4;

my $semSTDOUT :shared;
my $Q = new Thread::Queue;

my @threads = map async {
    my $tid = threads->tid;
    while( my $file = $Q->dequeue ) {
        open my $fh, '<', $file or warn ( "$file:$!"  ) and next;
        while( <$fh> ) {
            next unless m[$ARGV[0]];
            lock $semSTDOUT;
            print;
        }
        close $fh;
    }
}, 1 .. $THREADS;

$Q->enqueue( glob $ARGV[ 1 ] );
$Q->enqueue( (undef) x $THREADS );

$_->join for @threads;

__END__
c:\test>junk23 -THREADS=4 "Queue" *.pl >junk.dat

c:\test>head junk.dat
use Thread::Queue;
my $input_queue = Thread::Queue->new();
my $result_queue = Thread::Queue->new();
use Thread::Queue;
my $Q = Thread::Queue->new;
use Thread::Queue;
my $Q = new Thread::Queue;
use Thread::Queue;
my $Q = new Thread::Queue;
use Thread::Queue;