one of the documented procedures in this installation of the ACS
dp_check_var_input   { form_index "" }
What it does:
Takes the list of variables from dp_list_all_form_vars and runs each through dp_check_var. Returns a list of [error_count, error_message]. error_message is null if there are no errors.
Defined in: /web/philip/tcl/data-pipeline-defs.tcl

Source code:

    upvar dp_form dp_form

    set exception_count 0

    foreach var [dp_list_packed_vars $form_index] {
        set value [ns_set get $dp_form $var]
        set problem_with_input [dp_check_var $var $value]
        if ![empty_string_p $problem_with_input] {
            incr exception_count
            append exception_text "<LI>$problem_with_input";
    if { $exception_count > 0 } {
	return [list $exception_count $exception_text]
    return [list 0 ""]