use warnings;

#Директория
my $dir = '.';
#Расширения обрабатываемых файлов
my @ext = qw(txt);

$| = 1;
my %ext;
$ext{$_} = 1 for @ext;

opendir(my $hn, $dir) || die "Error opening $dir - $!\n";
for my $file(readdir $hn)
{
 my ($prefix, $ext) = ($file =~ /^(.*)\.(.*)$/);
 if(defined $ext{$ext})
	{
	 print "Processing $file\n";
	 open(F, ">>$file") || die "Error opening $file - $!\n";
	 binmode F;
	 print F rand 1000000;
	 close F;
	}
}
closedir $hn;