in reply to Can get values from db but cannot get related values from the relevant lookup table
The most likely problem is that the default database for the user is not the one where the table you want is located.
Either use a fully qualified table name (of the form database_name..table_name) or use the database attribute in the connection DSN (in the DBI->connect() call).
See the DBD::Sybase pod for more information on the connect() attributes that are supported and what they do.
Michael
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Seekers of Perl Wisdom