SGScript - meta-object sketch

// BEFORE
global sgs_evalspec_env =
{
    array = array,
    dict = dict,
    map = map,
    vec2 = vec2,
};
function sgs_evalspec( file, env )
{
    global _G;
    envbk = _G;
    pcall = _G.pcall;
    eval_file = _G.eval_file;
    sys_backtrace = _G.sys_backtrace;
    _G = get_merged( env, sgs_evalspec_env );

    errmsg = null;
    errstack = null;
    pcall(function sgs_evalspec_trycode() use( file, eval_file )
    {
        eval_file( file );
    },
    function sgs_evalspec_errhandler( code, msg ) use( errmsg, errstack, sys_backtrace )
    {
        errmsg = msg;
        errstack = sys_backtrace( true );
    });

    _G = envbk;

    return !errmsg, errmsg, errstack;
}
// AFTER
function sgs_evalspec( file, env )
{
    global _G;
    envbk = _G;
    _G = clone( env );
    metaobj_set( _G, envbk );

    errmsg = null;
    errstack = null;
    pcall(function sgs_evalspec_trycode()
    {
        eval_file( file );
    },
    function sgs_evalspec_errhandler( code, msg ) use( errmsg, errstack )
    {
        errmsg = msg;
        errstack = sys_backtrace( true );
    });

    _G = envbk;

    return !errmsg, errmsg, errstack;
}