code:

#!usr/bin/perl -w
system("cls");
sub newrand(){
my $rand;
	for ($i=0;$i<5;$i++){
		$rand .= int(rand(9));
	}
return $rand;
}


print "Folder? ";
$target = <STDIN>;
chomp $target;
opendir(TARGET, $target) or die "Invalid target directory\n";
@contents = readdir(TARGET);
@contents = grep(/\..{3}$/,@contents);
@oldcontents = @contents;
foreach (@contents){
	if ($_=~m/^\d{5}(.*)/){
	$_ = $1;
	$_ = newrand().$_;
	}
	else {
	$_ = newrand().$_;
	}
}
chdir($target);
for ($i = 0;$i<=$#contents;$i++){
rename($oldcontents[$i],$contents[$i]);
}


$"="\n";
$no = scalar @contents;
print "$no items renamed";