And, IIUC, the test script should accept '1000e-36' as correct when NV precision is 64 bits

Alternatively (and since you're already using POSIX) you should get the result you expected, if you replace the log() calls with POSIX::log10(). That way both numerator and divisor should be exact (for these particular inputs), as should also be the result of the division ... irrespective of the precision of the NV: 
$ perl -MPOSIX -le 'print POSIX::floor(POSIX::log10(1e-33) / POSIX::lo
+g10(1000));'
-11

[download]
Cheers,
Rob

In reply to Re^4: Portability of floor(log(N)) by syphilis
in thread Portability of floor(log(N)) by toolic

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