diff --git a/src/main.cpp b/src/main.cpp
index b27a5dc..c66e2ff 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -65,6 +65,9 @@ struct Lambda : Data {
 
 enum class locs { EVAL_START, EVAL_OP_FIN, EVAL_TOP_ARG, APPLY };
 
+enum class special_indef_eval {NONE, PROGN};
+
+
 struct Registers {
     std::variant<size_t, Data *, Cell> Exp;
     size_t args_front;
@@ -85,6 +88,8 @@ struct Registers {
 
     std::variant<size_t, Data *, Cell> R;
     Env E;
+
+	special_indef_eval screen = special_indef_eval::NONE;
 };
 
 struct Machine {
@@ -101,7 +106,7 @@ struct Machine {
         reg.E.builtin.insert("+");
         reg.E.builtin.insert("-");
         reg.E.builtin.insert("lambda");
-        reg.E.builtin.insert("block");
+        reg.E.builtin.insert("progn");
         reg.E.builtin.insert("print");
     }
 
@@ -153,6 +158,7 @@ struct Machine {
             }
             case locs::EVAL_OP_FIN: {
                 reg.op = reg.R; // save op
+				reg.screen = special_indef_eval::NONE;
 				if (Symbol * c = dynamic_cast<Symbol*>(std::get<Data*>(reg.op))) {
 					if(c->data == "lambda") {
 						reg.args_left = 0;
@@ -163,6 +169,9 @@ struct Machine {
 						break;
 
 					}
+					if(c->data == "progn") {
+						reg.screen = special_indef_eval::PROGN;
+					}
 				}
                 reg.args_left = mem[((Fork *)std::get<Data *>(reg.Exp))->data].cdr;
 				reg.args_current = 0;
@@ -183,12 +192,22 @@ struct Machine {
                     }
                     mem[reg.args_current].d = std::get<Data*>(reg.R);
                 }
-                if (reg.args_left != 0) {
+                if (reg.args_left != 0) { //args left
+					auto onlyoneleft = mem[reg.args_left].cdr == 0;
                     reg.argflag = true;
-                    stack.push_back(reg);
+
+					bool newframe = false;
+                    if (reg.screen == special_indef_eval::NONE
+						|| (reg.screen == special_indef_eval::PROGN && !onlyoneleft)) {
+						stack.push_back(reg);
+						newframe = true;
+
+					}
                     reg.D = mem[reg.args_left].d;
                     reg.args_left = mem[reg.args_left].cdr;
-					stack.back().args_left = reg.args_left;
+					if (newframe) {
+						stack.back().args_left = reg.args_left;
+					}
                     reg.RP = locs::EVAL_START;
                 } else {
                     reg.RP = locs::APPLY; // all args ready
@@ -293,12 +312,15 @@ struct Machine {
             l->f = mem[mem[cdr].cdr]; // mem[f->data];
             // std::cout <<"got lambd" << std::endl;
             return newCell(l);
-        } else if (fname == "block") {
+        } else if (fname == "progn") {
 			Data * out = NULL;
 			while (cdr != 0) {
 				out = (mem[cdr].d);
 				cdr = mem[cdr].cdr;
 			}
+			if (out == NULL) {
+				throw "progn with one arg";
+			}
 			return newCell(out);
 			
 		} else if (fname == "print") {
@@ -463,7 +485,7 @@ int main() {
 	m.reg.E.builtin.insert("*");
     m.reg.E.builtin.insert("-");
     m.reg.E.builtin.insert("lambda");
-    m.reg.E.builtin.insert("block");
+    m.reg.E.builtin.insert("progn");
     m.reg.E.builtin.insert("print");
 
     //m.ListPrint(m.mem[exp]);