Do you mean installing the module failed due to failing tests?

If so, try:

$ cpan
cpan> force install Digest::MD5::Reverse
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This will install it regardless of failed tests. Then, read its documentation and post again if you need help.

Update: there's nothing to it, you just pass an MD5 hash represented with ASCII characters ('A5F218'... instead of "\xa5\xf2\x18") to the reverse_md5() function. A simple script that lets you pass hashes from the command line:

use strict;
use warnings;
use Digest::MD5::Reverse;
die "Usage: $0 <md5 hash in ascii>\n" unless @ARGV;
my $md5       = shift;
my $plaintext = reverse_md5($md5);
print( defined $plaintext ? "$md5\t$plaintext" : "NOTFOUND", "\n" );
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The scary thing is I recognized the hash in the docs as being the hash of the string 'foo' without passing it to reverse_md5()... :|