I think you're looking for bind_param, it goes something like this:

use DBI qw(:sql_types);
$sth->bind_param( 1, $number, SQL_INTEGER );
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That would bind the first return column return from the statement to $number as an SQL_INTEGER. It should be noted that you need to make sure to import :sql_types when you use DBI, if you need further details check the DBI docs and look for bind_param (sorry, can't for the life of me remember how to link to the perldocs).