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Welcome to the MetaScript wiki! For now, the wiki contains a few non-trivial insights on writing meta.

Short statements

//? if (NODE)
buffer.writeInt8(offset, value);
//? else
view.setInt8(value, offset);

This will actually work without using curly braces as long as there is just one line following, because each source line is wrapped by a dedicated write(...) call, resulting in the following meta program:

if (NODE)
  write('buffer.writeInt8(offset, value);\n');
else
  write('view.setInt8(value, offset);\n');

White-spaces and line breaks

The MetaScript compiler makes sure to retain any white spaces and line breaks with one important exception: If a meta line or block, which is not a ?= expression, is the only contents of a line, the entire line will be skipped. Let's modify the example from above to demonstrate why this is useful:

if (true) {
    //? if (NODE)
    buffer.writeInt8(offset, value);
    //? else
    view.setInt8(value, offset);
}

The result of the above will not contain any white spaces or new lines where the meta statements are, like for NODE=true:

if (true) {
    buffer.writeInt8(offset, value);
}

Which looks much cleaner.

If you explicitly require indentation, you may use either a ?= expression, the __ variable or even call the indent(str:string, indent:string|number):string utility manually. Example:

// This will be indented (it's a ?= expression):
    //?= 'var i=0;'
// Just like this (it uses manual indentation):
    //? write(indent('var j=0;\n', 4));
// Or this (it prepends __):
    //? write(__+'var k=0;\n');
// But this will not:
    //? write('var k=0;\n');

Results in:

// This will be indented (it's a ?= expression):
    var i=0;
// Just like this (it uses manual indentation):
    var j=0;
// Or this (it prepends __):
    var k=0;
// But this will not:
var k=0;

The __ variable

When inspecting the generated meta program, you will notice that the variable __ is used quite frequently. It stores the indentation level of the last meta block processed. For example ...

//? if (NODE)
    //? include("node-stuff.js");
//? else
    //? include("browser-stuff.js");

... will indent the contents of the included files by '    ' (four spaces), just like before //?, while ...

/*? if (NODE)
    include("node-stuff.js");
else
    include("browser-stuff.js"); */

will not, just like before /*?. When creating custom utility functions, it's of course safe to use this variable on your own.