diff --git a/Makefile b/Makefile
index 709ab72..186cbcb 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,7 @@ SHELL = /bin/sh
 CFLAGS = -std=c99 -pedantic -Wextra -Os
 LDFLAGS = -lc
 
-OBJECTS = asm.o io.o ir.o lex.o lex/indent.o main.o parse.o x86encode.o
+OBJECTS = asm.o io.o ir.o lex.o lex/indent.o lang.o main.o parse.o x86encode.o
 
 .PHONY: passc
 passc: .bin $(OBJECTS)
diff --git a/src/ir.c b/src/ir.c
index 61f940c..12d81db 100644
--- a/src/ir.c
+++ b/src/ir.c
@@ -7,8 +7,10 @@
 #include "ir.h"
 
 #include <assert.h>
+#include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -45,12 +47,13 @@ void init(var* argc, var* argv, var* env) {
     *argc = stack_depth++;
 }
 
-label enter(uint32_t retc) {
+void enter(void) {
     assert(stack_frame < MAX_STACK_FRAMES);
     struct stack_frame frame = { stack_depth, label_depth };
     stack_frames[stack_frame] = frame;
     stack_frame++;
-    return declare(retc);
+    // exit label
+    declare(0);
 }
 
 void leave(var* args) {
@@ -68,6 +71,12 @@ label declare(uint32_t argc) {
     return label_depth++;
 }
 
+label declare_exit(uint32_t argc) {
+    label label = stack_frames[stack_frame].label_depth;
+    labels[label].argc = argc;
+    return label;
+}
+
 void define(label l, var* args) {
     struct label* label = &labels[l];
     label->definition = here;
@@ -114,6 +123,11 @@ var lit(uint64_t lit) {
     return stack_depth++;
 }
 
+var lit_string(char* str) {
+    fprintf(stderr, "error: string literals not yet implemented\n");
+    exit(1);
+}
+
 var sub(var subtrahend, var minuend) {
     // TODO: use modr/m
     load_var(AX, subtrahend);
diff --git a/src/ir.h b/src/ir.h
index 9aec2de..3548e54 100644
--- a/src/ir.h
+++ b/src/ir.h
@@ -20,15 +20,13 @@ void init(var* argc, var* argv, var* env);
 ///
 /// This also generates a new label corresponding with the end of the block,
 /// which will be automatically defined when you call `leave`.
-label enter(uint32_t retc);
+void enter(void);
 
 /// Leave a block.
 ///
 /// This will restore the context to how it was when `enter` was called,
-/// plus the return values declared by the call to `enter`.
-void leave(var* args);
-
-label declare_continue(uint32_t retc);
+/// plus the return values declared by the call to `declare_continue`.
+void leave(var* rets);
 
 /// Declare a new label in the innermost block.
 ///
@@ -36,7 +34,13 @@ label declare_continue(uint32_t retc);
 /// This label must be called with the given number of arguments.
 label declare(uint32_t argc);
 
-/// Define a label in the innermost block, automatically terminating
+//// Declare an exit label for the surrounding block.
+///
+/// Calling this label will exit the surrounding blocks.
+/// The usual restrictions for labels apply.
+label declare_exit(uint32_t retc);
+
+// Define a label in the innermost block, automatically terminating
 /// any previous labels.
 ///
 /// All variables defined prior to the beginning of this block will be in scope.
@@ -63,6 +67,9 @@ void jump_if(label label, var cond, var* args);
 /// Integer literal.
 var lit(uint64_t lit);
 
+/// String literal.
+var lit_string(char* str);
+
 /// Subtraction.
 var sub(var subtrahend, var minuend);
 
diff --git a/src/lang.c b/src/lang.c
new file mode 100644
index 0000000..d12fca7
--- /dev/null
+++ b/src/lang.c
@@ -0,0 +1,558 @@
+#include "ir.h"
+#include "lang.h"
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define MAX_CONTEXT 32
+#define MAX_ASSIGNMENTS 256
+#define MAX_ARGUMENTS 256
+#define MAX_OPERATORS 256
+
+struct assignment {
+    char* name;
+    var ref;
+};
+
+enum block_state {
+    BLOCK_CLEAN,
+    BLOCK_ASSIGN,
+    BLOCK_EXPR,
+};
+
+struct block_crumb {
+    enum block_state state;
+    uint32_t assignment_count;
+    struct assignment assignments[MAX_ASSIGNMENTS];
+    var final;
+};
+
+enum if_state {
+    IF_COND,
+    IF_THEN,
+    IF_ELSE,
+};
+
+struct if_crumb {
+    enum if_state state;
+    label then;
+    label else_;
+    label end;
+};
+
+enum loop_state {
+    LOOP_CLEAN,
+    LOOP_CVAR_INIT,
+    LOOP_BODY,
+};
+
+struct loop_crumb {
+    enum loop_state state;
+    char* label_name;
+    label next;
+    label exit;
+    uint32_t assignment_count;
+    var initializers[MAX_ASSIGNMENTS];
+    struct assignment assignments[MAX_ASSIGNMENTS];
+};
+
+struct expr_crumb {
+    uint32_t argument_count;
+    uint32_t operator_count;
+    var arguments[MAX_ARGUMENTS];
+    enum operator_ operators[MAX_OPERATORS];
+};
+
+enum crumb_type {
+    BLOCK_CRUMB,
+    IF_CRUMB,
+    LOOP_CRUMB,
+    EXPR_CRUMB,
+    JUMP_CRUMB,
+};
+
+union crumb_data {
+    struct block_crumb block;
+    struct if_crumb if_;
+    struct loop_crumb loop;
+    struct expr_crumb expr;
+    label jump;
+};
+
+struct crumb {
+    enum crumb_type type;
+    union crumb_data data;
+};
+
+static uint32_t context_depth = 1;
+static struct crumb context[MAX_CONTEXT];
+
+static char* copy_str(char* str) {
+    unsigned long len = strlen(str);
+    char* new = malloc(len * sizeof(char) + 1);
+    memcpy(new, str, len);
+    new[len] = 0;
+    return new;
+}
+
+static void push(struct crumb crumb) {
+    context[context_depth] = crumb;
+    context_depth++;
+}
+
+static void push_new_block(void) {
+    union crumb_data data;
+    struct block_crumb block = {
+        .state = BLOCK_CLEAN,
+        .assignment_count = 0,
+        .final = (var) -1,
+    };
+    data.block = block;
+    struct crumb crumb = {
+        .type = BLOCK_CRUMB,
+        .data = data,
+    };
+    push(crumb);
+}
+
+static void push_new_expr(void) {
+    struct expr_crumb exprc = {
+        .argument_count = 0,
+        .operator_count = 0,
+    };
+    union crumb_data data;
+    data.expr = exprc;
+    struct crumb crumb = {
+        .type = EXPR_CRUMB,
+        .data = data,
+    };
+    push(crumb);
+}
+
+static void push_new_jump(label label) {
+    union crumb_data data;
+    data.jump = label;
+    struct crumb crumb = {
+        .type = JUMP_CRUMB,
+        .data = data,
+    };
+    push(crumb);
+}
+
+static void push_argument(var ref) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == EXPR_CRUMB);
+    struct expr_crumb exprc = ctx.data.expr;
+    if (exprc.argument_count > MAX_ARGUMENTS) {
+        fprintf(stderr, "error: exceeded maximum number of arguments in expression\n");
+        exit(1);
+    }
+    exprc.arguments[exprc.argument_count] = ref;
+    exprc.argument_count++;
+}
+
+static void push_cvar_name(char* name) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == LOOP_CRUMB);
+    struct loop_crumb loopc = ctx.data.loop;
+    if (loopc.assignment_count == MAX_ASSIGNMENTS) {
+        fprintf(stderr, "error: exceed maximum number of assignments in loop cvars\n");
+        exit(1);
+    }
+    loopc.assignments[loopc.assignment_count].name = copy_str(name);
+}
+
+static void push_cvar(var ref) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == LOOP_CRUMB);
+    struct loop_crumb loopc = ctx.data.loop;
+    if (loopc.assignment_count > MAX_ASSIGNMENTS) {
+        fprintf(stderr, "error: exceed maximum number of assignments in loop cvars\n");
+        exit(1);
+    }
+    loopc.initializers[loopc.assignment_count] = ref;
+    loopc.assignment_count++;
+}
+
+static var lookup_assignment(
+    uint32_t assignment_count,
+    struct assignment* assignments,
+    char* name
+) {
+    for (uint32_t i = assignment_count; i > 0; i--) {
+        struct assignment asgn = assignments[i - 1];
+        if (strcmp(asgn.name, name) == 0) {
+            return asgn.ref;
+        }
+    }
+    return (var) -1;
+}
+
+static var lookup_var(char* name) {
+    for (uint32_t i = context_depth; i > 0; i--) {
+        struct crumb ctx = context[i - 1];
+        var ref = (var) -1;
+        switch (ctx.type) {
+            case LOOP_CRUMB:
+                if (ctx.data.loop.state != LOOP_BODY) {
+                    break;
+                }
+                ref = lookup_assignment(
+                    ctx.data.loop.assignment_count,
+                    ctx.data.loop.assignments,
+                    name
+                );
+                break;
+            case BLOCK_CRUMB:
+                ref = lookup_assignment(
+                    ctx.data.block.assignment_count,
+                    ctx.data.block.assignments,
+                    name
+                );
+                break;
+            default:
+                continue;
+        }
+        if (ref != (var) -1) {
+            return ref;
+        }
+    }
+    fprintf(stderr, "name resolution error: unknown variable %s\n", name);
+    exit(1);
+}
+
+enum label_type {
+    NEXT_LABEL,
+    EXIT_LABEL,
+    RETURN_LABEL,
+};
+
+static const char* label_type_name(enum label_type type) {
+    switch (type) {
+        case NEXT_LABEL:
+            return "next";
+        case EXIT_LABEL:
+            return "exit";
+        case RETURN_LABEL:
+            return "return";
+    }
+}
+
+static label lookup_label(enum label_type type, char* name) {
+    for (uint32_t i = context_depth; i > 0; i--) {
+        struct crumb ctx = context[i - 1];
+        switch (ctx.type) {
+            case LOOP_CRUMB:
+                if (name == NULL || strcmp(name, ctx.data.loop.label_name) == 0) {
+                    if (type == NEXT_LABEL) {
+                        return ctx.data.loop.next;
+                    }
+                    if (type == EXIT_LABEL) {
+                        return ctx.data.loop.exit;
+                    }
+                }
+                break;
+            default:
+                continue;
+        }
+    }
+    if (name == NULL) {
+        fprintf(stderr, "name resolution error: no %s label in scope\n", label_type_name(type));
+    } else {
+        fprintf(stderr, "name resolution error: unknown label %s\n", name);
+    }
+    exit(1);
+}
+
+void enter_block(void) {
+    struct crumb ctx = context[context_depth - 1];
+    switch (ctx.type) {
+        case BLOCK_CRUMB:
+            // we should have seen a stmt_assign or stmt_expr first,
+            // either of which pushes an expr crumb.
+            assert(0);
+        case EXPR_CRUMB: {
+            // this block is purely a scope/sequencing thing
+            // with no special semantics
+            break;
+        }
+        case IF_CRUMB: {
+            struct if_crumb ifc = ctx.data.if_;
+            switch (ifc.state) {
+                case IF_COND:
+                    assert(0);
+                case IF_THEN:
+                    define(ifc.then, NULL);
+                    break;
+                case IF_ELSE:
+                    define(ifc.else_, NULL);
+                    break;
+            }
+            break;
+        }
+        case LOOP_CRUMB: {
+            struct loop_crumb loopc = ctx.data.loop;
+            assert(loopc.state == LOOP_CLEAN);
+            loopc.state = LOOP_BODY;
+            var args[MAX_ASSIGNMENTS];
+            define(loopc.next, args);
+            // TODO NOTE: is this the correct order?
+            for (uint32_t i = 0; i < loopc.assignment_count; i++) {
+                loopc.assignments[i].ref = args[i];
+            }
+            break;
+        }
+        default:
+            assert(0);
+    }
+    push_new_block();
+}
+
+void stmt_assign(char* name) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == BLOCK_CRUMB);
+    struct block_crumb blockc = ctx.data.block;
+    assert(blockc.state == BLOCK_CLEAN);
+    if (blockc.assignment_count == MAX_ASSIGNMENTS) {
+        fprintf(stderr, "error: exceeded maximum number of assignments in block\n");
+        exit(1);
+    }
+    blockc.state = BLOCK_ASSIGN;
+    blockc.assignments[blockc.assignment_count].name = copy_str(name);
+    push_new_expr();
+}
+
+void stmt_expr(void) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == BLOCK_CRUMB);
+    struct block_crumb blockc = ctx.data.block;
+    assert(blockc.state == BLOCK_CLEAN);
+    blockc.state = BLOCK_EXPR;
+    push_new_expr();
+}
+
+void exit_block(void) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == BLOCK_CRUMB);
+    struct block_crumb blockc = ctx.data.block;
+    assert(blockc.state == BLOCK_CLEAN);
+    var ret = blockc.final;
+    if (ret == (var) -1) {
+        // TODO: better way to handle empty blocks
+        ret = lit(0);
+    }
+    context_depth--;
+    ctx = context[context_depth - 1];
+    switch (ctx.type) {
+        case EXPR_CRUMB: {
+            push_argument(ret);
+            break;
+        }
+        case IF_CRUMB: {
+            struct if_crumb ifc = ctx.data.if_;
+            assert(ifc.state != IF_COND);
+            jump(ifc.end, &ret);
+            break;
+        }
+        case LOOP_CRUMB: {
+            // unlike with `if`, there is no `exit_loop`, so we do clean-up here.
+            struct loop_crumb loopc = ctx.data.loop;
+            assert(loopc.state == LOOP_CLEAN);
+            jump(loopc.exit, &ret);
+            context_depth--;
+            for (uint32_t i = 0; i < loopc.assignment_count; i++) {
+                free(loopc.assignments[i].name);
+            }
+            leave(&ret);
+            push_argument(ret);
+            break;
+        }
+        default:
+            assert(0);
+    }
+    for (uint32_t i = 0; i < blockc.assignment_count; i++) {
+        free(blockc.assignments[i].name);
+    }
+}
+
+void exit_expr(void) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == EXPR_CRUMB);
+    struct expr_crumb exprc = ctx.data.expr;
+    assert(exprc.argument_count > 0);
+    if (exprc.operator_count > 0 || exprc.argument_count > 1) {
+        // TODO FIXME
+        fprintf(stderr, "error: I don't know how to evaluate exprs yet\n");
+        exit(1);
+    }
+    var ret = exprc.arguments[0];
+    context_depth--;
+    ctx = context[context_depth - 1];
+    switch (ctx.type) {
+        case BLOCK_CRUMB: {
+            struct block_crumb blockc = ctx.data.block;
+            blockc.final = ret;
+            switch (blockc.state) {
+                case BLOCK_CLEAN:
+                    assert(0);
+                case BLOCK_EXPR:
+                    break;
+                case BLOCK_ASSIGN:
+                    blockc.assignments[blockc.assignment_count].ref = ret;
+                    blockc.assignment_count++;
+                    break;
+            }
+            break;
+        }
+        case IF_CRUMB: {
+            struct if_crumb ifc = ctx.data.if_;
+            assert(ifc.state == IF_COND);
+            jump_if(ifc.then, ret, NULL);
+            jump(ifc.else_, NULL);
+            ifc.state = IF_THEN;
+            break;
+        }
+        case EXPR_CRUMB:
+            push_argument(ret);
+            break;
+        case LOOP_CRUMB: {
+            struct loop_crumb loopc = ctx.data.loop;
+            assert(loopc.state == LOOP_CVAR_INIT);
+            push_cvar(ret);
+            loopc.state = LOOP_CLEAN;
+            break;
+        }
+        case JUMP_CRUMB: {
+            // TODO FIXME: this is *completely wrong* for `next`!
+            label label = ctx.data.jump;
+            jump(label, &ret);
+            // TODO: better way to handle returning impossible value
+            push_argument(ret);
+            break;
+        }
+    }
+}
+
+void enter_if(void) {
+    enter();
+    label then = declare(0);
+    label else_ = declare(0);
+    label end = declare_exit(1);
+    struct if_crumb ifc = {
+        .state = IF_COND,
+        .then = then,
+        .else_ = else_,
+        .end = end,
+    };
+    union crumb_data data;
+    data.if_ = ifc;
+    struct crumb ctx = {
+        .type = IF_CRUMB,
+        .data = data,
+    };
+    push(ctx);
+    push_new_expr();
+}
+
+void exit_if(void) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == IF_CRUMB);
+    struct if_crumb ifc = ctx.data.if_;
+    switch (ifc.state) {
+        case IF_COND:
+            assert(0);
+        case IF_THEN: {
+            define(ifc.else_, NULL);
+            var ret = lit(0);
+            jump(ifc.end, &ret);
+            break;
+        }
+        case IF_ELSE:
+            break;
+    }
+    var ret;
+    leave(&ret);
+    push_argument(ret);
+}
+
+void enter_loop(char* label_name) {
+    enter();
+    label exit = declare_exit(1);
+    struct loop_crumb loopc = {
+        .state = LOOP_CLEAN,
+        .label_name = copy_str(label_name),
+        .assignment_count = 0,
+        .exit = exit
+    };
+    union crumb_data data;
+    data.loop = loopc;
+    struct crumb ctx = {
+        .type = LOOP_CRUMB,
+        .data = data,
+    };
+    push(ctx);
+}
+
+void cvar_pass(char* name) {
+    push_cvar_name(name);
+    push_cvar(lookup_var(name));
+}
+
+void cvar_init(char* name) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == LOOP_CRUMB);
+    struct loop_crumb loopc = ctx.data.loop;
+    loopc.state = LOOP_CVAR_INIT;
+    push_cvar_name(name);
+    push_new_expr();
+}
+
+void expr_next(char* label) {
+    push_new_jump(lookup_label(NEXT_LABEL, label));
+    push_new_expr();
+}
+
+void expr_exit(char* label) {
+    push_new_jump(lookup_label(EXIT_LABEL, label));
+    push_new_expr();
+}
+
+void expr_return(void) {
+    push_new_jump(lookup_label(RETURN_LABEL, NULL));
+    push_new_expr();
+}
+
+void enter_group(void) {
+    push_new_expr();
+}
+
+void exit_group(void) {
+    // exit_expr is sufficient
+}
+
+void expr_op(enum operator_ op) {
+    struct crumb ctx = context[context_depth - 1];
+    assert(ctx.type == EXPR_CRUMB);
+    struct expr_crumb exprc = ctx.data.expr;
+    if (exprc.operator_count > MAX_OPERATORS) {
+        fprintf(stderr, "error: exceeded maximum number of operators in expression\n");
+        exit(1);
+    }
+    exprc.operators[exprc.operator_count] = op;
+    exprc.operator_count++;
+}
+
+void expr_string(char* string) {
+    push_argument(lit_string(string));
+}
+
+void expr_integer(int64_t num) {
+    push_argument(lit((uint64_t) num));
+}
+
+void expr_var(char* var) {
+    push_argument(lookup_var(var));
+}
diff --git a/src/lang.h b/src/lang.h
new file mode 100644
index 0000000..d493d22
--- /dev/null
+++ b/src/lang.h
@@ -0,0 +1,32 @@
+#ifndef LANG_H
+#define LANG_H
+
+#include "lex.h"
+
+void enter_block(void);
+void stmt_assign(char* name);
+void stmt_expr(void);
+void exit_block(void);
+
+void exit_expr(void);
+
+void enter_if(void);
+void exit_if(void);
+
+void enter_loop(char* label);
+void cvar_pass(char* name);
+void cvar_init(char* name);
+
+void expr_next(char* label);
+void expr_exit(char* label);
+void expr_return(void);
+
+void enter_group(void);
+void exit_group(void);
+
+void expr_op(enum operator_ op);
+void expr_string(char* string);
+void expr_integer(int64_t num);
+void expr_var(char* var);
+
+#endif
diff --git a/src/parse.c b/src/parse.c
index 872590f..f08974b 100644
--- a/src/parse.c
+++ b/src/parse.c
@@ -192,6 +192,10 @@ void parse(void) {
                     push(ST_EXPR);
                     break;
                 }
+                if (tok.type == TOK_OPEN_BLOCK) {
+                    push(ST_BLOCK);
+                    continue;
+                }
                 syntax_error("expected expression");
             case ST_EXPR_CONT:
                 if (is_expr(tok)) {