my $path;
BEGIN {
   # Code that determines the path and stores it in $path.
   $path = "/www/domain/cgi-bin";
}
use lib $path;

##</code><code>##

use lib do {
   # Code that determines the path and returns it.
   "/www/domain/cgi-bin"
};

##</code><code>##

sub get_lib_path {
   # Code that determines the path and returns it.
   return "/www/domain/cgi-bin";
}

use lib get_lib_path();

##</code><code>##

# Hardcoded
use lib "/www/domain/cgi-bin";