Looking for someone who have knowledge with EXIM and PERL

Its about embedded perl in exim configuration file. we grab random ip and host in [login to view URL] using perl subroutine which exists in [login to view URL] this is the syntax: [login to view URL] the problem now is with setting primary_hostname variable from perl which is not working and setting only the literal so if we try to call perl function {perl{subroutine}} for primary_hostname var it sets only the literal '{perl{subroutine}}' as the value rather than getting from function i tested the code is in [login to view URL] where perl access exim variables using Exim::expand_string('$primary_hostname') thie $primary_hostname is the same which is in [login to view URL] but possible "expand_string" needs to be some other function.