use strict;
use File::Copy qw ( move );
my $dirname = "./temp"; # dir you want to open;
my $iterator = 0;
opendir (DIRHANDLE, $dirname) or die "could not open dir: $!";
foreach (readdir(DIRHANDLE)) {
	#need to add path
	my $filename = $dirname . "/$_";
	next unless -f $filename;
	move ($filename, $dirname . "/" . $iterator++) or warn "could not rename file";
}