C:\_32>perl -V:archname
archname='MSWin32-x86-multi-thread-64int';

C:\_32>perl -le "print $]";
5.024000

C:\_32>perl -le "$d = unpack 'd', pack 'Q', 0x7ff0000000000001;print $d; printf '%f', $d;"
NaN
NaN

##</code><code>##

NaN
7ff8000000000001

##</code><code>##

NaN
7ff0000000000001

##</code><code>##

NaN
7ff8000000000001