opendir my $dh, '/path/to/files', or die ...;
while( my file = readdir $dh ) {
    next unless $file =~ m[\.xml$];
    # do something with the file
}
closedir $dh;

##</code><code>##

#! perl -slw
use strict;
require 5.008;
use threads qw[yield];
use threads::shared;
use Thread::Queue;
use vars qw[$N];

die "Usage: $0 [-N=nn] dir .*\.xml" unless @ARGV == 2;

$N ||= 100;

my $signal : shared =  0;
my $Q = Thread::Queue->new();

sub readdir_asynch {
	my ($dir, $mask) = @_;
	print $mask;
	opendir my $dh, $dir
		or die "Couldn't open $dir";
	while( not $signal ) {
		yield if $Q->pending > $N;
		my $file = readdir( $dh );
		last unless defined $file;
		$Q->enqueue( $dir . '/' . $file ) if $file =~ m[^$mask$];
	}
	$Q->enqueue( "QUITING!!" );
}

my $thread = threads->create( \&readdir_asynch, $ARGV[0], $ARGV[1] );
yield;

while( ( my $file = $Q->dequeue ) ne 'QUITING!!' ) {
	printf "%s [%d]\n", $file, -S $file;
}

$thread->join;