use constant {
    SIGNBIT => 0x8000_0000_0000_0000,
    EXPBITS => 0x7FF0_0000_0000_0000,
    SIGBITS =>    0xF_FFFF_FFFF_FFFF,
    INDBITS =>    0x8_0000_0000_0000,
};

sub asHex{
    my $bin = unpack 'Q', pack 'd', $_[X];
    return "-0x1.#IND000000000p+0" if $bin == NEG_IND;
    my $sign = ( $bin & SIGNBIT ) ? '-' : ' ';
    my $exp  = ( ( $bin & EXPBITS ) >> 52 );
    my $mant = $bin & SIGBITS;
    if( $exp == 2047 ) {
        return $sign . "0x1.#INF000000000p+0" unless $mant;
        return $sign . ( $mant < INDBITS ? "0x1.#SNAN00000000p+0" : "0x1.#QNAN00000000p+0" );
    }
    $exp -= 1023;
    my $hid  = $exp == -1023 ? ( ++$exp, 0 ) : 1;

    sprintf "%s0x%1u.%013xp%+d", $sign, $hid, $mant, $exp;
}