// A hypothetical scanner class
struct _Scan {
    int !x;
    u8[~] buf;
    new _Scan={ u8[~] b -> buf=b; };
    // Skip whitespace
    val skip = { ->
        while( buf[x] <= ' ' )
            x++;
    };
    // Peek a character; if matched consume it, else false.
    val peek = { u8 c ->
        skip();
        if( buf[x] != c ) return false;
        x++;
        return true;
    };
};
!_Scan !s = new _Scan("  q");
return s.peek('q');