If you were submtting the form, it would work. Instead you are doing requests from JS based on information in the form. Your JavaScript only ever constructs requests with a single runs argument, so your script will never see more than one value for runs. Once you fix your JavaScript, the Perl side will work without modification.

The url should look like this

...?env=PROD&runs=2010-08-17 ----- 039733&runs=2010-08-17 ----- 039753
[download]

(Improperly escaped for readability.)