#!/usr/bin/perl

use DB_File;
use CGI 'param';

print "Content-type: text/plain\n\n";

my $filename = '/path/to/database';

tie %hash, "DB_File", $filename, O_RDWR|O_CREAT;
print 'thisvar: ', $hash{'thisvar'}, "\n";

$hash{'thisvar'} = param('webvar'); # modifies from form value

untie %hash;