It seems to work for me on MySQL 4.1 using $dbh instead of $sp->dbh: 
use strict;
use warnings;

use DBI;
my $dbh = DBI->connect( 'DBI:mysql:test', 'foo', 'bar' ) or die;
my $lon = -0.232323127347249;
my $sql = qq| SELECT lon,lat,location_id FROM lat_long WHERE lon>= $lo
+n|;
my $sth = $dbh->prepare($sql);
$sth->execute();
print STDERR "Rows not using placeholders ".$sth->rows."\n";

$sql = qq| SELECT lon,lat,location_id FROM lat_long WHERE lon >= ?|;
$sth = $dbh->prepare($sql);
$sth->execute($lon);
print STDERR "Rows using placeholders ".$sth->rows."\n";
__END__

[download]
create table lat_long(lon double not null, lat double not null, locati
+on_id integer);
insert into lat_long (location_id, lat, lon) values(44977, 48.3547, 11
+.7875);
insert into lat_long (location_id, lat, lon) values(53280, 48.1369, 11
+.5456);
insert into lat_long (location_id, lat, lon) values(53281, 48.1394, 11
+.5454);
insert into lat_long (location_id, lat, lon) values(53282, 47.6869, 11
+.7609);
insert into lat_long (location_id, lat, lon) values(53283, 48.3547, 11
+.7875);
insert into lat_long (location_id, lat, lon) values(60105, 48.3547, 11
+.7875);
insert into lat_long (location_id, lat, lon) values(80766, 48.3507, 11
+.7328);
insert into lat_long (location_id, lat, lon) values(71776, 48.1435, 11
+.5574);
insert into lat_long (location_id, lat, lon) values(65883, 48.1269, 11
+.6363);
insert into lat_long (location_id, lat, lon) values(65884, 48.1515, 11
+.6178);

[download]
$ perl 656378.pl
Rows not using placeholders 10
Rows using placeholders 10

[download]
Update Tue Dec 11 14:48:09 CET 2007: Re-ran using data supplied by ropey, still the same results.
--
Andreas

In reply to Re: Placeholders and Negative Numbers.. by andreas1234567
in thread Placeholders and Negative Numbers.. by ropey

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