http://www.perlmonks.org?node_id=942532


in reply to multiple selections in the same field using Mechanize

Setting a select field with multiple values allowed is documented at http://search.cpan.org/~abeltje/Win32-IE-Mechanize-0.009/lib/Win32/IE/Mechanize.pm#$ie-%3Eselect%28_$name,_\@values_%29:

$ie->select( $name, \@values ) Given the name of a select field, set its value to the value specified. If the field is not <select multiple> and the $value is an array, only the first value will be set. Passing $value as a hash with an n key selects an item by number (e.g. {n = 3> or {n = 2,4}>). The numbering starts at 1. This applies to the current form (as set by the form() method or defaulting to the first form on the page).
So,
$ie->select( 'parms', [ 'var1', 'var2' ]); or @multi_values = ('var1','var2'); $ie->select( 'parms', \@multi_values);