#! perl -slw
use strict;
use threads;
use Thread::Queue;

sub worker {
    my $Q = shift;
    my $count = 0;
    while( my $path = $Q->dequeue ) {
        chomp $path;
        my $file = do{ local( @ARGV, $/ ) = $path; <> };
        $count += () = $file =~ m[my]g;
    }
    return $count;
}


our $THREADS //= 4;

my $Q = new Thread::Queue;

my @workers = map{
    threads->create( \&worker, $Q );
} 1 .. $THREADS;

open DIR, '-|', q[ dir /s /b *.pl ] or die $!;
$Q->enqueue( <DIR> );
close DIR;

$Q->enqueue( (undef) x $THREADS );

my $count = 0;

$count += $_->join for @workers;
print "Found $count 'my's";

__END__
C:\test>921522-2.pl
Found 20825 'my's