rlm_perl - dbi - freetds works on radiusd -X but fails to sql connect in background

[nes pa]

I've changed the example.pl perl script so it 'use DBI;' to query a Sybase
server via freetds.
It works fine when running in foreground "radiusd -X" while testing.
However, if ran in background, the perl script gets triggered, but the dbi
connect fails:

my $dbh = DBI->connect("dbi:Sybase:server=*****", $user, $passwd,
{PrintError => 0});

Error: rlm_perl: perl_embed:: module = /etc/raddb/myperlscript.pm , func =
authenticate exit status= Unable for connect to server OpenClient message:
LAYER = (0) ORIGIN = (0) SEVERITY = (78) NUMBER = (41) Server ******,
database  Message String: Server is unavailable or does not exist.

* Tethereal shows that there is no network activity towards the Sybase
server.
* At first I guessed using user radiusd instead of root would sabotage
access to /etc/freetds.conf and/or freetds libraries, but changing
radiusd.conf so it keep root priviledges didn't help.
* I've been checking environment parameters between foreground and
background, but could not find a discriminator.
* Assuming some chroot'ing getting done by radiusd I have moved freetds.conf
inside /etc/raddb ( and /etc/raddb/etc ) to no avail.
* I have ran strace -f -p <pid> in the hope to see what the perlscript tries
to do when invoked by a radius request, but I only see it writing the error
to the /var/log/radius/radius.log
* Changed the hostname towards ip address in /etc/freetds.conf to avoid a
failing name resolving.

Any hints welcome for solution or better tools to debug/strace into the perl
script.
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