Web Development

I'll not give you concrete Apache config because

(1) I cannot test it from my environment
(2) I do not wish to encourage excessive spoon-feeding

Using authentication is a pretty basic area of Apache administration. You should be able to dig it up from other resources for exact details. I'll just give you pointers.

The main idea is, you first need to select the authentication mechanism - basic or digest authentication.

If your pages are served over HTTPS, that having a password essentially unencrypted will not be captured by eavesdropping, you can probably get by using basic authentication:
mod_auth_basic - Apache HTTP Server

If you need a bit more security, but a bit more tedious to set up, use digest authentication:
mod_auth_digest - Apache HTTP Server

Then you just plug one of the password stores for use with the authentication, in your case the LDAP one. You will then need configuration specific to LDAP.

This page essentially covers most of what you should know (concepts - you will need to find LDAP-specific info in other pages):
Authentication, Authorization and Access Control - Apache HTTP Server

Finally, in your Perl pages, check the REMOTE_USER environment variable. According to the CGI Specification, Apache should pass this username to you in case the user has been authenticated successfully. Do confirm this yourself.

If you use CGI object, you may retrieve it by $cgi->remote_user().

Just to give you a bit more supplement in case you still need some, although I think these should be really basic stuff a person who ever runs and uses an Apache should know already.

To apply the access restriction to a physical directory, use <Directory> and put all the access stuff inside the block. If you are referring to URL paths instead, use <Location>.

Configuration Sections - Apache HTTP Server

Depending on how your Apache is compiled, the mod_authnz_ldap may be compiled as module (.so) or compiled into the main Apache binary, or simply not compiled/installed on your system. You have to make sure it is usable (no one else can help you with this), and if being a .so, use a "LoadModule" in the Apache config to load it. There are plenty examples if you open the Apache config file.

At the end you can use "apachectl configtest" command to check your Apache configuration for correctness.