diff --git a/.gitignore b/.gitignore
index de63f45..8166c69 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,6 @@
 bin/flat
 y.*
-lex.yy.c
+lex.yy.?
 *.out
 tags
 *.o
diff --git a/Makefile b/Makefile
index 2ee24bd..9e74364 100644
--- a/Makefile
+++ b/Makefile
@@ -16,8 +16,12 @@
 
 CC = gcc
 CFLAGS = -Wall -Wextra -Wno-unused-parameter -O3 -std=c99 -pedantic -D_XOPEN_SOURCE
-YACC = bison -y -d -t -v
+
+YACC = bison
+YACC_FLAGS = -y -d -t -v
+
 LEX = flex
+LEX_FLAGS =
 
 LIBS = -I/usr/local/include -I/usr/include -L/usr/local/lib -L/usr/lib -lm
 OBJ_FILES = y.tab.o lex.yy.o src/eval.o src/str.o src/regexp.o src/cli.o \
@@ -77,13 +81,15 @@ malloc-debug: LIBS += -lefence
 malloc-debug: debug
 
 
-lex.yy.o: $(LEX_FILE)
-	$(LEX) $(LEX_FILE)
+lex.yy.c:
+	$(LEX) --header-file=lex.yy.h $(LEX_FLAGS) $(LEX_FILE)
+
+lex.yy.o: lex.yy.c $(LEX_FILE)
 	@echo "[CC -o] lex.yy.o"
 	@$(CC) -c $(CFLAGS) lex.yy.c -o lex.yy.o
 
-y.tab.o: $(YACC_FILE)
-	$(YACC) $(YACC_FILE)
+y.tab.o: lex.yy.c $(YACC_FILE)
+	$(YACC) $(YACC_FLAGS) $(YACC_FILE)
 	@echo "[CC -o] y.tab.o"
 	@$(CC) -c $(CFLAGS) y.tab.c -o y.tab.o
 
@@ -94,7 +100,7 @@ linker: $(OBJ_FILES)
 	@$(CC) -c $(CFLAGS) $< -o $@
 
 clean:
-	rm -rf y.* lex.yy.c $(OUT_FILE) $(OBJ_FILES)
+	rm -rf y.* lex.yy.c y.tab.c y.tab.h $(OUT_FILE) $(OBJ_FILES)
 
 install:
 	cp $(OUT_FILE) /usr/local/bin/
diff --git a/src/flathead.h b/src/flathead.h
index 80bbc00..b119592 100644
--- a/src/flathead.h
+++ b/src/flathead.h
@@ -251,7 +251,8 @@ eval_state * fh_new_state(int, int);
 js_val * fh_get_arg(js_args *, int);
 unsigned int fh_arg_len(js_args*);
 
-js_val * fh_eval_file(FILE *, js_val *, int);
+js_val * fh_eval_file(FILE *, js_val *);
+js_val * fh_eval_string(char *, js_val *);
 js_val * fh_try_get_proto(char *);
 
 bool fh_is_callable(js_val *);
diff --git a/src/grammar.y b/src/grammar.y
index 7792228..d0c2859 100644
--- a/src/grammar.y
+++ b/src/grammar.y
@@ -29,6 +29,7 @@
   #include <readline/history.h>
 #endif
 
+  #include "lex.yy.h"
   #include "src/flathead.h"
   #include "src/nodes.h"
   #include "src/eval.h"
@@ -99,10 +100,7 @@
   #define NEW_WITH(exp,stmt)         NEW_NODE(NODE_WITH_STMT,exp,stmt,0,0,0)
 
   void yyerror(const char *);
-  void yyrestart(FILE *);
-  int yylex(void);
   int yydebug;
-  FILE *yyin;
   int fh_get_input(char *, int);
   ast_node *root;
   eval_state *state;
@@ -1142,8 +1140,10 @@ fh_get_input(char *buf, int size)
       return 0;
     }
     strcpy(buf, line);
-    // Ghetto ASI
+
+    // Poor man's ASI:
     if (!strchr(buf, ';')) strcat(buf, ";");
+
     strcat(buf, "\n");
     free(line);
     add_history(buf);
@@ -1162,7 +1162,7 @@ fh_get_input(char *buf, int size)
 }
 
 js_val *
-fh_eval_file(FILE *file, js_val *ctx, int is_repl)
+fh_eval_file(FILE *file, js_val *ctx)
 {
   yyrestart(file);
   yyparse();
@@ -1174,6 +1174,20 @@ fh_eval_file(FILE *file, js_val *ctx, int is_repl)
   return res;
 }
 
+js_val *
+fh_eval_string(char *string, js_val *ctx)
+{
+  void *buffer = yy_scan_string(string);
+  yyparse();
+
+  if (fh->opt_print_ast) 
+    print_node(root, true, 0);
+
+  js_val *res = fh_eval(ctx, root);
+  yy_delete_buffer(buffer);
+  return res;
+}
+
 int
 main(int argc, char **argv)
 {
@@ -1227,10 +1241,10 @@ main(int argc, char **argv)
       // continue. Use setjmp here and longjmp in `fh_error` to simulate
       // exception handling.
       if (!setjmp(fh->jmpbuf))
-        DEBUG(fh_eval_file(source, fh->global, true));
+        DEBUG(fh_eval_file(source, fh->global));
     }
   } else {
-    fh_eval_file(source, fh->global, false);
+    fh_eval_file(source, fh->global);
   }
 
   return 0;
diff --git a/src/lexer.l b/src/lexer.l
index 9b94e5c..c42b9f0 100644
--- a/src/lexer.l
+++ b/src/lexer.l
@@ -26,6 +26,8 @@
   int yycolumn = 1;
   int prev_token = 0;
   void yyuseraction(void);
+  YY_BUFFER_STATE yy_scan_string(const char *);
+  void yy_delete_buffer(YY_BUFFER_STATE);
 
   char * fh_extract_string(char *);
   void fh_parse_error(char *);
diff --git a/src/runtime/runtime.c b/src/runtime/runtime.c
index 32ad876..9992a6c 100644
--- a/src/runtime/runtime.c
+++ b/src/runtime/runtime.c
@@ -80,9 +80,9 @@ global_parse_float(js_val *instance, js_args *args, eval_state *state)
 js_val *
 global_eval(js_val *instance, js_args *args, eval_state *state)
 {
-  // TODO: implement
-  fh_error(state, E_ERROR, "eval is not yet implemented");
-  UNREACHABLE();
+  js_val *code = TO_STR(ARG(args, 0));
+  code->string.ptr[code->string.length] = '\0';
+  return fh_eval_string(code->string.ptr, state->ctx);
 }
 
 // gc()
@@ -108,7 +108,7 @@ global_load(js_val *instance, js_args *args, eval_state *state)
       fh_error(state, E_ERROR, "File could not be read");
 
     FILE *file = fopen(name->string.ptr, "r");
-    fh_eval_file(file, fh->global, false);
+    fh_eval_file(file, fh->global);
     fclose(file);
   }
   return JSUNDEF();
diff --git a/test/test_eval.js b/test/test_eval.js
new file mode 100644
index 0000000..158a002
--- /dev/null
+++ b/test/test_eval.js
@@ -0,0 +1,20 @@
+// test_eval.js
+// ------------
+// Note the unfortunate limitation that until ASI is added, statements within
+// strings passed to eval need to be semicolon-terminated.
+
+(this.load || require)((this.load ? 'test' : '.') + '/tools/assertions.js');
+
+
+test('eval without references', function() {
+  assertEquals(1,  eval('1;'));
+  assertEquals(4,  eval('2 + 2;'));
+  assertEquals(42, eval('(function() { return 42; });')());
+});
+
+test('eval with references', function() {
+  var x = 42;
+  assertEquals(x, eval('x;'));
+  assertEquals(f, eval('f;'));
+  function f() { return 'The f function'; };
+});
diff --git a/test/test_globals.js b/test/test_globals.js
index 0466833..e1dfcd6 100644
--- a/test/test_globals.js
+++ b/test/test_globals.js
@@ -53,23 +53,23 @@ test('global functions', function() {
     assertIsFunction(parseInt, 2);
 
     // without radix
-    assert(parseInt("42") === 42);
-    assert(parseInt("3.14") === 3);
+    assertEquals(42, parseInt("42"));
+    assertEquals(3,  parseInt("3.14"));
     assertNaN(parseInt("Not a number"));
 
     // with radix
-    assert(parseInt(" 0xF", 16) === 15);
-    assert(parseInt(" F", 16) === 15);
-    assert(parseInt("17", 8) === 15);
-    // FIXME: assert(parseInt(021, 8) === 15);
-    assert(parseInt("015", 10) === 15);
-    assert(parseInt(15.99, 10) === 15);
-    // FIXME: assert(parseInt("FXX123", 16) === 15);
-    assert(parseInt("1111", 2) === 15);
-    // FIXME: assert(parseInt("15*3", 10) === 15);
-    // FIXME: assert(parseInt("15e2", 10) === 15);
-    // FIXME: assert(parseInt("15px", 10) === 15);
-    assert(parseInt("12", 13) === 15);
+    assertEquals(15, parseInt(" 0xF", 16));
+    assertEquals(15, parseInt(" F", 16));
+    assertEquals(15, parseInt("17", 8));
+    // FIXME: assertEquals(15, parseInt(021, 8));
+    assertEquals(15, parseInt("015", 10));
+    assertEquals(15, parseInt(15.99, 10));
+    // FIXME: assertEquals(15, parseInt("FXX123", 16));
+    assertEquals(15, parseInt("1111", 2));
+    // FIXME: assertEquals(15, parseInt("15*3", 10));
+    // FIXME: assertEquals(15, parseInt("15e2", 10));
+    // FIXME: assertEquals(15, parseInt("15px", 10));
+    assertEquals(15, parseInt("12", 13));
     assertNaN(parseInt("Not a number", 10));
   });
 
@@ -82,7 +82,10 @@ test('global functions', function() {
   });
 
   test('eval(x)', function() {
+    // See also: test_eval.js
     assertIsFunction(eval, 1);
+    assertEquals(4,  eval('2 + 2;'));
+    assertEquals(42, eval('21 * 2;'));
   });
 
 });