DBI->connect ("dbi:Oracle:$ENV{ORACLE_SID}", $TGT_USER, $TGT_PASS) …

=>

DBI->connect ("dbi:Oracle:sid=$ENV{ORACLE_SID}", $TGT_USER, $TGT_PASS) …

or

DBI->connect ("dbi:Oracle:", $TGT_USER, $TGT_PASS) …