[Exim] Perl in Auth Config section (exim-3.34)

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Hi,
I want my server to use a perl subroutine for authenticating smtp users.
I built with AUTH_CRAM_MD5=yes and AUTH_PLAINTEXT=yes and EXIM_PERL=perl.o. I set up a simple perl script called /etc/exim.pl with a subroutine called mysubroutine that just appends some garbage to a text file (for testing purposes), and then I added perl_startup = '/etc/exim.pl' and perl_at_start = true, and it all seems to start up fine. Except for this:
$./exim -be
> ${perl{mysubroutine}{arg1}}
Failed: Undefined subroutine &main::mysubroutine called.
Any help would be appreciated.
Thanks,
Amir.

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