Are you sure the DSN is right? i.e., are you able to use $dbh for anything else? Since the do() returns 1, it sounds like a transaction issue, but i see that you have AutoCommit => 1 in there.. a blind stab, but try $dbh->commit after the do() ...

As for side notes, a couple things came to mind:

• Try to always use placeholders w/DBI:

  my $sql = qq~DELETE FROM `gates-post` WHERE id = ?~;
  my @bind = ( $dat[1] );
  $dbh->do($sql, {}, @bind);
  [download]

• SQL::Abstract may be of interest to avoid writing your own SQL
• Same with Class::DBI -- treat your rows as objects and never write any sql -- just a few lines of CDBI code.

(The last two may not be needed/appropriate in your case, but definitely very good tools to be aware of.)

Update: I just read jZed's post, which has the very good point about $rows .. I guess i assumed it was 1 -- you should print it to confirm if it's 1 or 0E0 .. if the latter, then i would turn attention to $dat1 and confirm that it really has the desired value..