Fix stale marker bug in labeled blocks

Root cause: Labeled blocks were not clearing the RuntimeControlFlowRegistry
when they exited, causing stale markers to affect subsequent labeled blocks.

This caused uni/variables.t to stop at test 56 because an eval with a labeled
block left a marker that interfered with later SKIP blocks.

Fix: Clear the registry when exiting any labeled block.

Changes:
- EmitBlock.java: Call RuntimeControlFlowRegistry.clear() when exiting labeled blocks
- skip_control_flow.t: Add test case #10 for stale marker bug

Results:
- skip_control_flow.t: all 10 tests pass ✓
- uni/variables.t: 66683/66880 (baseline maintained) ✓
- op/pack.t: baseline maintained ✓
- make: BUILD SUCCESSFUL ✓

Author: fglock

.gitignore

@@ -49,6 +49,11 @@ logs/
 .perlonjava_env_ready
 *.diff
 *.patch
+
+.windsurf/
+Image-ExifTool-13.44/
+dev/examples/DiagnoseBytecodeEstimation.pl
+dev/prompts/fix_pat_advanced_verifyerror.md
 # But allow patch files in import-perl5/patches/
 !dev/import-perl5/patches/*.patch
 

src/main/java/org/perlonjava/codegen/EmitBlock.java

@@ -150,6 +150,16 @@ public static void emitBlock(EmitterVisitor emitterVisitor, BlockNode node) {
 
         if (node.isLoop) {
             emitterVisitor.ctx.javaClassInfo.popLoopLabels();
+            
+            // Clear any stale markers when exiting a labeled block
+            // This prevents markers from affecting subsequent labeled blocks
+            if (node.labelName != null) {
+                mv.visitMethodInsn(Opcodes.INVOKESTATIC,
+                        "org/perlonjava/runtime/RuntimeControlFlowRegistry",
+                        "clear",
+                        "()V",
+                        false);
+            }
         }
 
         // Pop labels used inside the block

src/test/resources/unit/skip_control_flow.t

@@ -133,4 +133,20 @@ sub ok_tap {
     ok_tap($out eq 'AC', 'last LABEL3 exits LABEL3 block (2 frames, void context)');
 }
 
+# 10) Stale marker bug - labeled block in eval leaves marker
+{
+    my $out = '';
+    # This eval creates a labeled block that might leave a stale marker
+    eval "\${\x{30cd}single:\x{30cd}colon} = 'test'";
+    $out .= 'A';
+    
+    # This SKIP block should work normally, not be affected by stale marker
+    MYLABEL: {
+        $out .= 'B';
+        $out .= 'C';
+    }
+    $out .= 'D';
+    ok_tap($out eq 'ABCD', 'labeled block in eval does not leave stale marker');
+}
+
 print "1..$t\n";