diff --git a/src/main/java/com/google/devtools/build/lib/skylarkdebug/proto/skylark_debugging.proto b/src/main/java/com/google/devtools/build/lib/skylarkdebug/proto/skylark_debugging.proto
index a1066c3..cc0de17 100644
--- a/src/main/java/com/google/devtools/build/lib/skylarkdebug/proto/skylark_debugging.proto
+++ b/src/main/java/com/google/devtools/build/lib/skylarkdebug/proto/skylark_debugging.proto
@@ -66,14 +66,14 @@
   Stepping stepping = 2;
 }
 
-// A request to evaluate a Skylark expression in a thread's current environment.
+// A request to evaluate a Skylark statement in a thread's current environment.
 message EvaluateRequest {
   // The identifier of the thread in whose execution context the expression
   // should be evaluated.
   int64 thread_id = 1;
 
-  // The Skylark expression to evaluate.
-  string expression = 2;
+  // The Skylark statement to evaluate.
+  string statement = 2;
 }
 
 // A request to list the stack frames of a thread.
@@ -141,7 +141,7 @@
 
 // The response to an EvaluateRequest.
 message EvaluateResponse {
-  // The result of evaluating an expression.
+  // The result of evaluating a statement.
   Value result = 1;
 }
 
@@ -185,7 +185,8 @@
   }
   // An optional condition for the breakpoint. When present, the breakpoint will
   // be triggered iff both the primary condition holds and this expression
-  // evaluates to True.
+  // evaluates to True. It is unspecified how many times this expression will be
+  // evaluated, so it should be free of side-effects.
   string expression = 2;
 }
 
diff --git a/src/main/java/com/google/devtools/build/lib/skylarkdebug/server/SkylarkDebugServer.java b/src/main/java/com/google/devtools/build/lib/skylarkdebug/server/SkylarkDebugServer.java
index 93e833d..433f4ef 100644
--- a/src/main/java/com/google/devtools/build/lib/skylarkdebug/server/SkylarkDebugServer.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkdebug/server/SkylarkDebugServer.java
@@ -201,7 +201,7 @@
       long sequenceNumber, SkylarkDebuggingProtos.EvaluateRequest request)
       throws DebugRequestException {
     return DebugEventHelper.evaluateResponse(
-        sequenceNumber, threadHandler.evaluate(request.getThreadId(), request.getExpression()));
+        sequenceNumber, threadHandler.evaluate(request.getThreadId(), request.getStatement()));
   }
 
   /** Handles a {@code ContinueExecutionRequest} and returns its response. */
diff --git a/src/main/java/com/google/devtools/build/lib/skylarkdebug/server/ThreadHandler.java b/src/main/java/com/google/devtools/build/lib/skylarkdebug/server/ThreadHandler.java
index 585d581..6f92949 100644
--- a/src/main/java/com/google/devtools/build/lib/skylarkdebug/server/ThreadHandler.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkdebug/server/ThreadHandler.java
@@ -235,7 +235,7 @@
     }
   }
 
-  SkylarkDebuggingProtos.Value evaluate(long threadId, String expression)
+  SkylarkDebuggingProtos.Value evaluate(long threadId, String statement)
       throws DebugRequestException {
     Debuggable debuggable;
     synchronized (this) {
@@ -250,7 +250,7 @@
     // accessed in response to a client request, and requests are handled serially
     // TODO(bazel-team): support asynchronous replies, and use finer-grained locks
     try {
-      Object result = doEvaluate(debuggable, expression);
+      Object result = doEvaluate(debuggable, statement);
       return DebuggerSerialization.getValueProto("Evaluation result", result);
     } catch (EvalException | InterruptedException e) {
       throw new DebugRequestException(e.getMessage());
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Debuggable.java b/src/main/java/com/google/devtools/build/lib/syntax/Debuggable.java
index 4540f55..ee871e6 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Debuggable.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Debuggable.java
@@ -22,8 +22,8 @@
 /** A context in which debugging can occur. Implemented by Skylark environments. */
 public interface Debuggable {
 
-  /** Evaluates a Skylark expression in the adapter's environment. */
-  Object evaluate(String expression) throws EvalException, InterruptedException;
+  /** Evaluates a Skylark statement in the adapter's environment. */
+  Object evaluate(String statement) throws EvalException, InterruptedException;
 
   /**
    * Returns the stack frames corresponding of the context's current (paused) state.
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Environment.java b/src/main/java/com/google/devtools/build/lib/syntax/Environment.java
index 5b22906..d5b0d6c 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Environment.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Environment.java
@@ -29,6 +29,7 @@
 import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.Mutability.Freezable;
 import com.google.devtools.build.lib.syntax.Mutability.MutabilityException;
+import com.google.devtools.build.lib.syntax.Parser.ParsingLevel;
 import com.google.devtools.build.lib.util.Fingerprint;
 import com.google.devtools.build.lib.util.Pair;
 import com.google.devtools.build.lib.util.SpellChecker;
@@ -1169,15 +1170,31 @@
   }
 
   @Override
-  public Object evaluate(String expression) throws EvalException, InterruptedException {
-    ParserInputSource inputSource =
-        ParserInputSource.create(expression, PathFragment.create("<debug eval>"));
+  public Object evaluate(String contents) throws EvalException, InterruptedException {
+    ParserInputSource input =
+        ParserInputSource.create(contents, PathFragment.create("<debug eval>"));
     EvalEventHandler eventHandler = new EvalEventHandler();
-    Expression expr = Parser.parseExpression(inputSource, eventHandler);
+    Statement statement = Parser.parseStatement(input, eventHandler, ParsingLevel.LOCAL_LEVEL);
     if (!eventHandler.messages.isEmpty()) {
-      throw new EvalException(expr.getLocation(), eventHandler.messages.get(0));
+      throw new EvalException(statement.getLocation(), eventHandler.messages.get(0));
     }
-    return expr.eval(this);
+    // TODO(bazel-team): move statement handling code to Eval
+    // deal with the most common case first
+    if (statement.kind() == Statement.Kind.EXPRESSION) {
+      return ((ExpressionStatement) statement).getExpression().doEval(this);
+    }
+    // all other statement types are executed directly
+    Eval.fromEnvironment(this).exec(statement);
+    switch (statement.kind()) {
+      case ASSIGNMENT:
+      case AUGMENTED_ASSIGNMENT:
+        return ((AssignmentStatement) statement).getLValue().getExpression().doEval(this);
+      case RETURN:
+        Expression expr = ((ReturnStatement) statement).getReturnExpression();
+        return expr != null ? expr.doEval(this) : Runtime.NONE;
+      default:
+        return Runtime.NONE;
+    }
   }
 
   @Override