# list your headers
my @heading = qw[description billing_code user_id 
                 project_id bad_proj bad_bill bad_user];

# now prepare a statement *once*
my $sth = $dbh-<prepare('INSERT INTO temp_sheet ('
                        .join(',', @heading)
                        .') VALUES ('.
                        .join(',', map {'?'} @heading)
                        .')'
                       );

# now insert
foreach my $row (@fields) {
   $sth->execute( map { $row{$_} } @heading );
}