diff --git a/examples/high_order.fk b/examples/high_order.fk
new file mode 100644
index 0000000..717cdef
--- /dev/null
+++ b/examples/high_order.fk
@@ -0,0 +1,4 @@
+($ add (-> (x) (+ 1 x)))
+($ twice (-> (f x) (f (f x))))
+
+(assert= 6 (twice add 4))
\ No newline at end of file
diff --git a/libstd/lib.cpp b/libstd/lib.cpp
index ae5ca5d..50a4b6c 100644
--- a/libstd/lib.cpp
+++ b/libstd/lib.cpp
@@ -2,8 +2,11 @@
 #include "fun.hpp"
 #include "macro.hpp"
 
+Module* glob_mod;
+
 extern "C" void lib(Module& mod)
 {
+  glob_mod = &mod;
   mod.register_function("assert=", fkstd::assert_eq);
   mod.register_function("println", fkstd::println);
   mod.register_function("+", fkstd::add_int);
diff --git a/src/Module.hpp b/src/Module.hpp
index 63f5907..bc5ae48 100644
--- a/src/Module.hpp
+++ b/src/Module.hpp
@@ -18,6 +18,8 @@ namespace fk
     explicit Module(std::filesystem::path source_path);
     virtual ~Module();
 
+    std::shared_ptr<VM> vm() const { return m_vm; }
+
     void build();
 
     void import_std();
diff --git a/src/Program.cpp b/src/Program.cpp
index 4824b14..d16b38b 100644
--- a/src/Program.cpp
+++ b/src/Program.cpp
@@ -36,6 +36,7 @@ namespace fk
 
   size_t Program::add(std::shared_ptr<Constant> constant)
   {
+    assert(constant);
     for (size_t i=0; i<m_consts.size(); i++)
       {
         if (m_consts[i]->equals(*constant)
diff --git a/src/VM.cpp b/src/VM.cpp
index 7c07da8..25c162c 100644
--- a/src/VM.cpp
+++ b/src/VM.cpp
@@ -21,7 +21,8 @@ namespace fk
 
   void VM::run()
   {
-    while (m_pc < frame().program->size())
+    while (m_frames.empty() == false
+           && m_pc < frame().program->size())
       {
         Instr instr = frame().program->instr(m_pc);
 
@@ -75,10 +76,19 @@ namespace fk
                     pop();
                   }
               }
-
             auto value = m_frames.back().program->get_const(*ret);
+
             m_frames.pop_back();
-            push(frame().program->add(value));
+
+            if (m_frames.empty() == false)
+              {
+                push(frame().program->add(value));
+              }
+            else
+              {
+                m_return_const = value;
+              }
+
             m_pc++;
           } break;
 
@@ -92,10 +102,16 @@ namespace fk
               }
 
             auto ref_val = frame().program->get_const(pop());
+
             addr_t ref = std::get<addr_t>(ref_val->value());
 
             auto lambda = std::get<std::shared_ptr<Lambda>>(load_global(ref));
 
+
+            auto self = std::make_shared<Constant>(TYPE_REF,
+                                                   static_cast<size_t>(ref),
+                                                   ref_val->loc());
+
             Frame frame;
             frame.program = lambda->program();
             frame.ret_addr = m_pc;
@@ -107,9 +123,6 @@ namespace fk
                 store_local(i, args[i]);
               }
 
-            auto self = std::make_shared<Constant>(TYPE_REF,
-                                                   static_cast<size_t>(ref),
-                                                   ref_val->loc());
             store_local(args.size(), self);
 
             m_pc = 0;
@@ -144,7 +157,15 @@ namespace fk
 
           case OP_LOAD_LOCAL: {
             auto value = frame().locals[instr.param];
-            assert(value);
+
+            if (!value)
+              {
+                std::cerr << "cannot find value with ref '"
+                          << instr.param
+                          << "'" << std::endl;
+                abort();
+              }
+
             push(frame().program->add(value));
 
             m_pc++;
@@ -185,8 +206,41 @@ namespace fk
       }
   }
 
+  std::shared_ptr<Constant>
+  VM::call(std::shared_ptr<Lambda> lambda,
+           size_t ref,
+           std::vector<std::shared_ptr<Constant>> const& args,
+           Loc const& loc)
+  {
+    Frame frame;
+    frame.program = lambda->program();
+    frame.ret_addr = m_pc;
+    frame.stack_sz = m_stack.size();
+    m_frames.push_back(frame);
+
+    for (size_t i=0; i<args.size(); i++)
+      {
+        store_local(i, args[i]);
+      }
+
+    auto self = std::make_shared<Constant>(TYPE_REF,
+                                           static_cast<size_t>(ref),
+                                           loc);
+    store_local(args.size(), self);
+
+    m_pc = 0;
+
+    return nullptr;
+  }
+
   global_t VM::load_global(addr_t addr) const
   {
+    if (m_globals.find(addr) == std::end(m_globals))
+      {
+        std::cerr << "cannot find global " << addr << std::endl;
+        abort();
+      }
+
     return m_globals.at(addr);
   }
 
@@ -243,4 +297,39 @@ namespace fk
     m_stack.pop_back();
     return t;
   }
+
+  std::shared_ptr<Constant>
+  VM::run_lambda(VM const& parent,
+                 std::shared_ptr<Lambda> lambda,
+                 std::vector<std::shared_ptr<Constant>> args,
+                 size_t ref,
+                 Loc const& loc)
+  {
+    for (auto entry: parent.m_globals)
+      {
+        store_global(entry.first, entry.second);
+      }
+
+    auto self = std::make_shared<Constant>(TYPE_REF,
+                                           static_cast<size_t>(ref),
+                                           loc);
+    Frame frame;
+    frame.program = lambda->program();
+    frame.ret_addr = m_pc;
+    frame.stack_sz = m_stack.size();
+    m_frames.push_back(frame);
+
+    for (size_t i=0; i<args.size(); i++)
+      {
+        store_local(i, args[i]);
+      }
+
+    store_local(args.size(), self);
+
+    m_pc = 0;
+
+    run();
+
+    return m_return_const;
+  }
 }
diff --git a/src/VM.hpp b/src/VM.hpp
index d3b1fe5..505ef1d 100644
--- a/src/VM.hpp
+++ b/src/VM.hpp
@@ -30,6 +30,12 @@ namespace fk
     void mount(std::shared_ptr<Program> program);
     void run();
 
+    std::shared_ptr<Constant>
+    call(std::shared_ptr<Lambda> lambda,
+         size_t ref,
+         std::vector<std::shared_ptr<Constant>> const& args,
+         Loc const& loc);
+
     global_t load_global(addr_t addr) const;
     void store_global(addr_t addr, global_t value);
     size_t store_global(global_t value);
@@ -39,15 +45,23 @@ namespace fk
 
     std::string string() const;
 
+    void push(addr_t addr);
+    addr_t top();
+    addr_t pop();
+
+    std::shared_ptr<Constant>
+    run_lambda(VM const& parent,
+               std::shared_ptr<Lambda> lambda,
+               std::vector<std::shared_ptr<Constant>> args,
+               size_t ref,
+               Loc const& loc);
+
   private:
     addr_t m_pc = 0;
     std::vector<Frame> m_frames;
     std::vector<addr_t> m_stack;
     std::unordered_map<addr_t, global_t> m_globals;
-
-    void push(addr_t addr);
-    addr_t top();
-    addr_t pop();
+    std::shared_ptr<Constant> m_return_const;
   };
 }
 
diff --git a/src/main.cpp b/src/main.cpp
index 36e5adc..fe9a645 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -17,7 +17,7 @@ int main(int argc, char** argv)
 
       int opt_index = 0;
 
-      int c = getopt_long(argc, argv, "h", options, &opt_index);
+      int c = getopt_long(argc, argv, "hd", options, &opt_index);
 
       if (c == -1)
         {