#!/usr/bin/perl

use strict;
use warnings;

my $x = -666;
my $y = sprintf("%23.16e\n", $x);           # -6.6600000000000000e+02
if ($y =~ m/^(.+)e\+(\d+)$/) {
    printf("%23.16fD+%02d\n", $1/10, $2+1); # -0.6660000000000000D+03
}