use DBI;

my $pgh=DBI->connect("DSN for Postgres here");
my $orh=DBI->connect("DSN for Oracle here");

#set up statments into variables for both
eval{
  my $psh=$pgh->prepare($write_stmt);
  my $osh=$orh->prepare($read_stmt);
  $osh->execute( variable list here );
  $osh->bind_columns( \( $f1, $f2, $f3, ... ) );
  while($osh->fetch)
  {
    $psh->execute( $f1, $f2, $f3, ... );
  }
  $pgh->commit;
}
if($@)  # error handler goes here
{
  $pgh->rollback;
  print STDERR "Problem saving data\n";
}