502 when URLs contain spaces

I have IIS8.5 WS2012 and my sites uses Perl. Whenever I use a URL containing spaces it returns 502.2 Bad Gateway.
For example:

http://172.25.25.163:80/cgi/webhyd.pl?po=201001&st=Reports&sn=WEBREPORTS&t=PLT&j=FPL&h=Plot%20of%20Daily%20Flow%20Duration&cat=rs&lvl=1&tab=rspf_org

Tracing reveals:

The specified CGI application misbehaved by not returning a complete set of HTTP headers. The headers it did return are "

'st' is not recognized as an internal or external command, operable program or batch file.
'sn' is not recognized as an internal or external command, operable program or batch file.
't' is not recognized as an internal or external command, operable program or batch file.
'j' is not recognized as an internal or external command, operable program or batch file.
'h' is not recognized as an internal or external command, operable program or batch file.
cat: =rs: No such file or directory
'lvl' is not recognized as an internal or external command, operable program or batch file.
'tab' is not recognized as an internal or external command, operable program or batch file.
Content-Type: text/html; charset=utf-8

".

I am at my wits end. Please help me.