C:\>perl -wle "$d = unpack 'D>', pack 'D>', 2.9; print $d"
Invalid type 'D' in pack at -e line 1.

##</code><code>##

C:\>perl -wle "$ld = unpack 'D>', pack 'D>', 2.9; print $ld"
2.9

##</code><code>##

D  A float of long-double precision in native format.
   (Long doubles are available only if your system supports
   long double values. Raises an exception otherwise.
   Note that there are different long double formats.)