my $dbh = ...;
   ...
   { # enclosing block for transaction
#       local $dbh->{'AutoCommit'} = 1;
# UPDATE - thanks Corion
       local $dbh->{'AutoCommit'} = 0;
       local $dbh->{'PrintError'} = 0;

       # do the transaction queries
       ...
       $dbh->commit();
   }