Option 1:

Before any use of DBI/DBD,

BEGIN {
   $ENV{ORACLE_HOME}     = "...";
   $ENV{LD_LIBRARY_PATH} = "...";
}
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I think I heard this doesn't work. Something about a clone of the environment getting creating by the C runtime library before this, and this is what Oracle uses?

Option 2:

Set the environment before calling Perl.

ORACLE_HOME=... LD_LIBRARY_PATH=... perl ...
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You could use a loader script for this.

Option 3:

Make the Perl script itself the loader script.

BEGIN {
   my $oracle_home     = "...";
   my $ld_library_path = "...";
   if ($ENV{ORACLE_HOME} ne $oracle_home
   || $ENV{LD_LIBRARY_PATH} ne $ld_library_path
   ) {
      $ENV{ORACLE_HOME}     = "...";
      $ENV{LD_LIBRARY_PATH} = "...";
      exec { $^X } $^X, $0, @ARGV;
   }
}
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