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>= $lon|;
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__

##</code><code>##

create table lat_long(lon double not null, lat double not null, location_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);

##</code><code>##

$ perl 656378.pl
Rows not using placeholders 10
Rows using placeholders 10