Please could someone explain the problem for me.

In Impl/Makefile.PL we find:

$opt = $Config{ar} =~ /ar\.exe$/ ? '-ru ' : '/out:';
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Change that to:

$opt = $Config{ar} =~ /^ar/ ? '-ru ' : '/out:';
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That gets you past the problem you struck, but there's another change you need to make.
In Impl/Impl.h, line 10 is:

typedef unsigned long ULONG_PTR;
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Remove that line (or comment it out).
Once those changes have been made, the module then builds and tests fine for me on 64-bit Strawberry Perl 5.20.0.
(I built, tested and installed it by manually running "perl Makefile.PL", "dmake test" and "dmake install".)

Cheers,
Rob