Let's say you have a form with one option being a numeric user ID with a name of 'id' and the other option a color named 'color' that you want to set for that user ID (let's say you're setting a color preference). The following (untested) example assumes that the table is called 'preferences' and that the appropriate field names are 'id' and 'color'.

#!/usr/bin/perl -wT
use strict;

use CGI;
use DBI; # I'm just assuming that you use the DBI module for
         # database connectivity.  Substitute another module
         # as appropriate.

my $query = new CGI;

# The regexes are for "taint checking"
$query->param('color') =~/^([a-zA-Z]+)$/ or die "Bad data in color";
my $color = $1;
$query->param('id')    =~/^([0-9]+)$/    or die "Bad data in id";
my $id = $1;

my $database = 'preferences';

my $sql = "UPDATE $database SET color='$color' WHERE id='$id'";

# now, connect to the database and execute the SQL.
[download]

Regarding the taint checking, see perlsec for details. If you are unfamiliar with connecting to a database with Perl, please read A Short Guide to DBI.

Cheers,
Ovid

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use CGI::SQL;

$db = new CGI::SQL($DBH,'item_');
$rv = $db->insert_from_param('item');
[download]