Manipulate slice or specific element of range and return range

[Timoses]

Hey,

I'm struggling to find a way to achieve this. I've looked through 
std.algorithm but didn't find anything.. Maybe I'm blind.

What I would like to do is filter out all spaces in a string and 
change the front letter to lower case:

     string m = "My Capital String";
     string lower = m
         .filter!(c => c != ' ')
         .<executeAt>!(0, c => c.toLower) // executeAt does not 
exist
         .array.to!string;
     assert(lower == "myCapitalString");

or sth like

     m.filter!(...)
         .map!((element, int index) {
             if (index == 0)
                 return element.toLower;
             else
                 break; // stop since we are done manipulating 
range
         });

Anyway to do this?