For convenience, copy the following into /usr/local/bin/dirrename and make it executable:

#!/usr/bin/perl -w

# Copyright (c) 2008 jlh (jlh at gmx dot ch)
#
# This bit of code is released under the GPL version 2 or (at your option) any
# later version.

use strict;
use warnings;

my $get_tmp_name_n = 0;

sub get_tmp_name {
	my $tmp;

	while (1) {
		$get_tmp_name_n++;
		$tmp = ".__dirrename_tmp_${get_tmp_name_n}__";
		last if !-e $tmp;
	}

	return $tmp;
}

# check if we have write access to .

if (!-w '.') {
	print "I do not have write access to this directory.\n";
	exit 1;
}

# read the list of files to rename

opendir my $h, '.' or die;
my @list = sort grep { !/^\./ } readdir $h;
closedir $h;

# write it to a file

my $tmp = "/tmp/pid.$$";
open $h, '>', $tmp or die;
print $h join("\n", @list), "\n";
close $h;

# let the user edit it

my $editor = $ENV{EDITOR} || 'vi';
system("$editor '$tmp'");

# read it back in

open $h, '<', $tmp or die;
my @newlist = map { my $a = $_; chomp $a; $a; } <$h>;
close $h;
unlink $tmp;

# compare

if (@list != @newlist) {
	print "Number of lines has been changed!";
	exit 1;
}

# check for errors

my $error = 0;

my %from;
$from{$_}++ for @list;
my %to;
$to{$_}++ for @newlist;

for (keys %to) {
	if ($to{$_} > 1) {
		print "error: more than one file wants to rename to '$_'\n";
		$error = 1;
	}
	if (!exists $from{$_} and -e $_) {
		print "error: target exists already: $_\n";
		$error = 1;
	}
}

exit $error if $error;

# build a trivial strategy to rename the file (rename all files to a temporary
# name, then all temporary names are renamed to the target names; this avoids
# cycles and dependencies)

my @strategy;

for (0 .. $#list) {
	my ($old, $new) = ($list[$_], $newlist[$_]);
	next if $old eq $new;
	my $tmp = &get_tmp_name;
	unshift @strategy, [ $old, $tmp ];
	push @strategy, [ $tmp, $new ];
}

# now optimize this strategy.  this avoids unnecessary renaming but takes more
# time to plan.  it would probably be faster without doing this, but it was fun
# to write it.  :)

while (1) {

	my $done_something = 0;

	for (my $i = 0; $i < @strategy; $i++) { # regular loop because we splice @strategy in here
		my $target = $strategy[$i][1];
		my $j = undef;
		for ($i + 1 .. $#strategy) {
			if ($strategy[$_][1] eq $target) {
				die "Assertion failure...\n";
			}
			if ($strategy[$_][0] eq $target) {
				$j = $_;
				last;
			}
		}
		if (defined $j) {
			my $target_target = $strategy[$j][1];

			# see if we can merge $strategy[$i] and $strategy[$j] into $strategy[$i]...

			my $ok = 1;
			for ($i + 1 .. $j - 1) {
				if ($strategy[$_][0] eq $target_target or $strategy[$_][1] eq $target_target) {
					$ok = 0;
					last;
				}
			}

			if ($ok) {
				# ...yes we can, do it
				#print "reducing chain: $strategy[$i][0] -> $target -> $target_target (up)\n";
				$strategy[$i][1] = $target_target;
				splice @strategy, $j, 1;
				next;
			} 

			# we couldn't, try to merge $strategy[$i] and $strategy[$j] into $strategy[$j] instead

			my $from = $strategy[$i][0];
			$ok = 1;
			for ($i + 1 .. $j - 1) {
				if ($strategy[$_][0] eq $from or $strategy[$_][1] eq $from) {
					$ok = 0;
					last;
				}
			}

			if ($ok) {
				# ...yes we can, do it
				#print "reducing chain: $strategy[$i][0] -> $target -> $target_target (down)\n";
				$strategy[$j][0] = $from;
				splice @strategy, $i, 1;
				$i--;
				next;
			}
		}
	}

	last unless $done_something;
}

# execute it

print "Performing " . scalar(@strategy) . " rename operations\n";

for (@strategy) {
	#print "$_->[0] -> $_->[1]\n";
	rename $_->[0], $_->[1];
}