got the annoying Error: only one entry point main is allowed again, this time I wanted a real fix rather then leaving a comment out main, found this pattern:

foo.d
#!rdmd
import bar;

void main(){
	foobar(3);
}

bar.d
#!rdmd -version=localmain
void foobar(int i){
    import std;
    i.writeln;
}

version(localmain){
    void main(){
        foobar(7);
}}

% ./bar.d
7
% ./foo.d
3