Compiling and installing version 4.15 on Windows needs further tweak in Makefile.PL, The following line reports a error on Windows if I use Microsoft Visual Studio as compiler ("|" is Unix flavor, Not MS)
open(H_IN, "-|", "cpp", $curl_h) and $has_cpp++;
Just replace it with next line.
open(H_IN, "<", $curl_h);
That does the trick.
Once it is installed with ActiveState perl 5.12.2 on Windows. All 3 modules WWW::Curl::Multi, WWW::Curl::Share, WWW::Curl::Easy work good.