If you're wanting to use this now, you don't necessarily need a module. There appear to be command-line versions of all the programs in the suite (both Windows and *nix), allowing you to use backticks to simply do....

my $data = `swetest -b1.1.2002 -n1 -s1 -fPLBRS -pp -eswe`;
[download]

or whatever. (Data from the test page)

Should you need deeper interaction with the code, all the C source is available on their site. Looking at the amount of calculation going on in the code, you're probably better off wrapping this somehow (Inline::C / SWIG / XS ), rather than re-writing in Perl.

Hope this helps,
Ben.