Not only is mdillon's solution correct, it's also much more
efficient as each factorial is simply one multiply on the
previous one, whereas calling the function each time means a lot more
work is being done.
Now the reason for the failure is that the Math::NumberCruncher
function overflows for 171!. Unfortunately it returns '1.#INF' which
Perl happily treats as 1.0 in your division, so you simply divide by
one from that point on, not making much more progress.
Update: While Math::NumberCruncher
does not use BigFloats for it's factorial function, it does
already use the Math::BigFloat module
for storing its very large version of $PI (though strangely BigFloats are not used
in calculations with that $PI so it's probably pointless...), so it is a
trivial matter to patch Math::NumberCruncher
to use a BigFloat for the factorial. This is of course for occasional uses
as for an iterative use of factorial mdillon's answer is still
much faster.

I'd like to be able to assign to an luser
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