[horde] Install Horde 5 fails with new server

[Louis-Philippe Allard]

All steps and pre-requisites were successfully installed thanks to the PHP
IRC folks and their knowledge!  Now I am trying to install Horde Webmail
and it fails.

I have followed the steps provided at
http://www.horde.org/apps/webmail/docs/INSTALL to the letter with

pear channel-discover pear.horde.org
pear install horde/horde_role
pear run-scripts horde/horde_role
pear install -a -B horde/webmail

but when I went to run the command webmail-install I got:

PHP Warning:  require_once(PEAR/Config.php): failed to open stream: No such
file or directory in /usr/bin/webmail-install on line 15

Warning: require_once(PEAR/Config.php): failed to open stream: No such file
or directory in /usr/bin/webmail-install on line 15
PHP Fatal error:  require_once(): Failed opening required 'PEAR/Config.php'
(include_path='.:/php/includes:/usr/lib/php') in /usr/bin/webmail-install
on line 15

Fatal error: require_once(): Failed opening required 'PEAR/Config.php'
(include_path='.:/php/includes:/usr/lib/php') in /usr/bin/webmail-install
on line 15

So whats the deal with it?  I've searched the maillist and found a similar
situation, the person was adviced to restart fresh which I did but got to
the same point...

Can someone provide guidance to get this running???

Thanks!!