Set global immutables from main/getopt?

[Andrew Klaassen]

I thought it'd be a good idea to set global immutables from args 
passed to main().  When I do this:

import io = std.stdio;

immutable string abc;

void foo() {
  io.writeln(abc);
}

void main(string[] args) {
  abc = args[1];
  foo();
}


...I get the compiler error: "Error: can only initialize const 
member abc inside constructor".  When I do this:


import io = std.stdio;

void foo() {
  io.writeln(abc);
}

void main(string[] args) {
  immutable string abc = args[1];
  foo();
}


...I get the compiler error: "Error: undefined identifier abc".

Is there any workaround, or am I attempting a 
stupidity/impossibility?

Thanks.

Andrew