Look at the part after the last @ symbol:

%31%30%38%35%33%30%35%31%36%35
[download]

Anything before the @ should be considered a Basic Authentication username, IIRC.
URI::Escape should help with this, which gave me an integer, which needs to be converted to a proper IPV4 address. This is only partially tested:

#!/usr/local/bin/perl -w
use strict;

use URI::Escape;
my $URL = "%31%30%38%35%33%30%35%31%36%35";
print $URL . "\n";
my $int_ip = uri_unescape($URL);
print $int_ip . "\n";
my @octets;
my $register = $int_ip;

while(int($register)) {
  unshift(@octets, $register % 256);
  $register /= 256;
}

for(@octets) {
  print;
  print ".";
}
print "\n";
[download]

This is pretty rough, but it should do the job. I included the print statements so you can see exactly what it's doing. Feel free to customize (cannibalize) for your own not-so-evil purposes. Reverse DNS is up to you.

Update: I just cleaned up the code a bit.

HTH,

--isotope