La extensión readline para php no está en Debian (ni en Ubuntu) por problemas de licencia. Entre tantos bugreports, blogposts y opiniones varias he encontrado esta frase: «Licensing issues. Readline is GPL, and we can't link with GPL libraries without violating their license.»

Las expresiones regulares son (ver: wikipedia, ).

http://www.regular-expressions.info/
http://regexlib.com/
http://www.amk.ca/python/howto/regex/
http://weblogtoolscollection.com/regex/regex.php
http://www.php.net/manual/en/book.pcre.php
http://www.php.net/manual/en/book.regex.php
http://www.php.net/manual/en/reference.pcre.pattern.differences.php

It is still a work in progress...

http://drupal.org/project/spip2drupal