sub double_to_bin {
   my $n = shift;

   my ( $s, $e, $m ) =
      unpack "a1 a11 a52",
         unpack "B64",
            pack "d>", $n;

   $e = oct( "0b$e" );
   if ( $e == 0x7FF ) {
      if ( $m =~ /^0+\z/ ) {
         return $s ? "-inf" : "+inf" ;
      } else {
         return "nan";
      }
   }

   my $n_bin = ( $e ? "1" : "" ) . $m;

   $e -= 1023;
   if ( $e < 0 ) {
      $n_bin = "0." . ( "0" x ( -$e - 1 ) ) . $n_bin;
   } else {
      my $z = ( $e + 1 ) - length( $n_bin );
      if ( $z >= 0 ) {
         $n_bin .= "0" x $z;
      } else {
         substr( $n_bin, $e+1, 0, "." );
      }
   }

   $n_bin =~ s/^0+(?=[01])//;
   if ( $n_bin =~ /\./ ) {
      #$n_bin =~ s/0+\z//;
      $n_bin =~ s/\.\z//;
   }

   $n_bin = ( $s ? "-" : "" ) . $n_bin;

   return $n_bin;
}

##</code><code>##

$ perl -e'printf "%.751g\n", unpack "d", pack "Q", 1'
4.940656458412465441765687928682213723650598026143247644255856825006755072702087518652998363616359923797965646954457177309266567103559397963987747960107818781263007131903114045278458171678489821036887186360569987307230500063874091535649843873124733972731696151400317153853980741262385655911710266585566867681870395603106249319452715914924553293054565444011274801297099995419319894090804165633245247571478690147267801593552386115501348035264934720193790268107107491703332226844753335720832431936092382893458368060106011506169809753078342277318329247904982524730776375927247874656084778203734469699533647017972677717585125660551199131504891101451037862738167250955837389733598993664809941164205702637090279242767544565229087538682506419718265533447265625e-324