#perl -e 'use Config;print "long doubles\n" if $Config{d_longdbl} eq "define";'
long doubles

##</code><code>##

# perl -e 'use Config;if ($Config{uselongdouble} eq "define") {print "long doubles by default\n";} else {print "not default? How to use???\n"}'
not default? How to use???