You need to install the LWP perl module (libwww-perl) and then install csf

[root@server22 csf]# sh install.sh

Configuring for OS

Checking for perl modulesfailed
You need to install the LWP perl module (libwww-perl) and then install csf
[root@server22 csf]#

To fix the error, install libwww-perl

yum install perl-libwww-perl