use strict;
use warnings;
use File::Find;

my $dir = 'C:\Download';
my $max_size = 25*1024*1024; #25 Mo

opendir DIR, $dir or die;

my @large_files = grep {stat("$dir/$_"))[7] > $max_size} readdir(DIR);

closedir DIR or die;

# or recursively
find( \&wanted, $dir );

sub wanted { 
	(stat)[7] > $max_size and push @large_files, $File::Find::name;
}