diff --git a/src/fh_builtins_arith.c b/src/fh_builtins_arith.c
index df8b43e..4391b90 100644
--- a/src/fh_builtins_arith.c
+++ b/src/fh_builtins_arith.c
@@ -331,6 +331,24 @@ static enum fh_error w_slash_mod(struct fh_thread_s *fh, const struct fh_word_s
   return FH_OK;
 }
 
+static enum fh_error w_mod(struct fh_thread_s *fh, const struct fh_word_s *w)
+{
+  (void) w;
+  enum fh_error rv;
+  uint32_t a = 0, b = 0;
+  TRY(ds_pop(fh, &b));
+  TRY(ds_pop(fh, &a));
+
+  if (b == 0) {
+    return FH_ERR_DIV_BY_ZERO;
+  }
+
+  uint32_t rem = a % b;
+
+  TRY(ds_push(fh, rem));
+  return FH_OK;
+}
+
 const struct name_and_handler fh_builtins_arith[] = {
     /* Arithmetics */
     {"base",    wp_const,          0, MAGICADDR_BASE},
@@ -349,6 +367,7 @@ const struct name_and_handler fh_builtins_arith[] = {
     {"/",       w_slash,           0, 0},
     {"abs",     w_abs,             0, 0},
     {"/mod",    w_slash_mod,       0, 0},
+    {"mod",     w_mod,             0, 0},
     {"invert",  w_invert,          0, 0},
     {"negate",  w_negate,          0, 0},
     {"0<",      w_zero_less,       0, 0},
diff --git a/src/fh_builtins_control.c b/src/fh_builtins_control.c
index db70574..93392f5 100644
--- a/src/fh_builtins_control.c
+++ b/src/fh_builtins_control.c
@@ -215,22 +215,22 @@ static enum fh_error wp_ij(struct fh_thread_s *fh, const struct fh_word_s *w)
 }
 
 const struct name_and_handler fh_builtins_control[] = {
-    {"i",         wp_ij,             0, 0},
-    {"j",         wp_ij,             0, 1},
-    {"if",        w_if,              1, 0},
-    {"else",      w_else,            1, 0},
-    {"then",      w_then,            1, 0},
-    {"recurse",   w_recurse,         1, 0},
-    {"do",        wp_do,             1, 0},
-    {"?do",       wp_do,             1, 1},
-    {"loop",      wp_loop,           1, 0},
-    {"leave",     w_leave,          1, 0},
-    {"loop+",     wp_loop,           1, 1},
-    {"begin",     w_begin,           1, 0},
-    {"while",     w_while,           1, 0},
-    {"repeat",    w_repeat,          1, 0},
-    {"again",     w_again,           1, 0},
-    {"until",     w_until,           1, 0},
+    {"i",       wp_ij,     0, 0},
+    {"j",       wp_ij,     0, 1},
+    {"if",      w_if,      1, 0},
+    {"else",    w_else,    1, 0},
+    {"then",    w_then,    1, 0},
+    {"recurse", w_recurse, 1, 0},
+    {"do",      wp_do,     1, 0},
+    {"?do",     wp_do,     1, 1},
+    {"loop",    wp_loop,   1, 0},
+    {"leave",   w_leave,   1, 0},
+    {"+loop",   wp_loop,   1, 1},
+    {"begin",   w_begin,   1, 0},
+    {"while",   w_while,   1, 0},
+    {"repeat",  w_repeat,  1, 0},
+    {"again",   w_again,   1, 0},
+    {"until",   w_until,   1, 0},
 
     { /* end marker */ }
 };
diff --git a/src/fh_builtins_system.c b/src/fh_builtins_system.c
index 6e966ea..c11ae0c 100644
--- a/src/fh_builtins_system.c
+++ b/src/fh_builtins_system.c
@@ -41,11 +41,22 @@ static enum fh_error w_bye(struct fh_thread_s *fh, const struct fh_word_s *w)
   return FH_OK;
 }
 
+static enum fh_error w_debug(struct fh_thread_s *fh, const struct fh_word_s *w)
+{
+  (void) w;
+  enum fh_error rv;
+  uint32_t val;
+  TRY(ds_pop(fh, &val));
+  fh_globals.verbose = val;
+  return FH_OK;
+}
+
 const struct name_and_handler fh_builtins_system[] = {
     {"depth",     w_depth,           0, 0},
     {"unused",    w_unused,          0, 0},
     {"reset",     w_reset,           1, 0},
     {"bye",       w_bye,             0, 0},
+    {"debug",     w_debug,           0, 0},
 
     { /* end marker */ }
 };
diff --git a/src/fh_builtins_text.c b/src/fh_builtins_text.c
index d62ffca..440258d 100644
--- a/src/fh_builtins_text.c
+++ b/src/fh_builtins_text.c
@@ -64,6 +64,18 @@ static enum fh_error w_dot(struct fh_thread_s *fh, const struct fh_word_s *w)
   return FH_OK;
 }
 
+static enum fh_error w_u_r(struct fh_thread_s *fh, const struct fh_word_s *w)
+{
+  (void) w;
+  enum fh_error rv;
+  uint32_t a = 0, n = 0;
+  TRY(ds_pop(fh, &n));
+  TRY(ds_pop(fh, &a));
+
+  FHPRINT("%*d", n, a);
+  return FH_OK;
+}
+
 static enum fh_error w_type(struct fh_thread_s *fh, const struct fh_word_s *w)
 {
   (void) w;
@@ -191,6 +203,7 @@ const struct name_and_handler fh_builtins_text[] = {
     {"cr",    wp_putc,      0, '\n'},
     {"space", wp_putc,      0, ' '},
     {"bl",    wp_const,     0, ' '},
+    {"u.r",   w_u_r,        0, 0},
     {"??",    w_debug_dump, 0, 0},
     {"emit",  w_emit,       0, 0},
     {"see",   w_see,        0, 0},
diff --git a/src/fh_runtime.c b/src/fh_runtime.c
index 164f890..4248abf 100644
--- a/src/fh_runtime.c
+++ b/src/fh_runtime.c
@@ -329,10 +329,14 @@ enum fh_error w_user_word(struct fh_thread_s *fh, const struct fh_word_s *w0)
       // R: index,limit
       TRY(rs_peek(fh, &limit));
 
+      LOG("+LOOP, i=%d, step %d, limit %d", fh->loop_i, val, limit);
+
       index0 = fh->loop_i;
       fh->loop_i += val;
 
-      if (index0 < limit == fh->loop_i < limit) { // boundary not crossed, continue
+      LOG("after add: %d", fh->loop_i);
+
+      if (((int32_t)index0 < (int32_t)limit) == ((int32_t)fh->loop_i < (int32_t)limit)) { // boundary not crossed, continue
         fh->execptr = instr->data; // go to beginning
       } else {
         // end of loop
diff --git a/src/main.c b/src/main.c
index d411b72..8bf2d23 100644
--- a/src/main.c
+++ b/src/main.c
@@ -78,6 +78,9 @@ int main(int argc, char *argv[])
       }
       /* reset state */
       fh_setstate(&fh, FH_STATE_INTERPRET, FH_SUBSTATE_NONE);
+      // reset stack pointers
+      fh.data_stack_top = 0;
+      fh.return_stack_top = 0;
     }
 
     FHPRINT("%s", prompt);