It's been a really long time since I used the Sybase DBD driver but I seem to remember that you need to create an entry in an interfaces file to map between a logical server name and the physical server name. Not sure what you mean by "TDS configuration."

If I remember how the interfaces file is configured correctly it looks something like:

[BILLING] 
host = 123.213.13.2
port = 1433
database = BILLING
user = USER
password = PASSWORD
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BEGIN{  $ENV{SYBASE}='/opt/sybase....handwaving here...';
}
use DBI;
my $dbh=DBI->connect('DBI:Sybase:server=BILLING') or die $DBI->errstr;
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