fix: prototype parsing, signature defaults, and utf8::upgrade regression

- isNamedUnaryPrototype: only match exactly "$" or "_" (length 1).
  Prototypes like ($;), (_;), ($;$) are list operators, not named unary.
  Fixes comp/proto.t tests 208-209 regression.

- _ prototype: allow zero arguments and default to $_ when no arg given.
  Fixes comp/uproto.t (0/32 -> 29/32).

- SignatureParser: parse default values at comma precedence instead of
  named-unary precedence. Allows ternary/comparison/logical ops in
  signature defaults like ($c = $x > 0 ? foo() : "").
  Fixes op/signatures.t (0/0 -> 643/908).

- utf8::upgrade: remove ($) prototype to match Perl 5 (no prototype).
  Without this, "utf8::upgrade my $x = ..." parsed incorrectly as
  named unary, taking only "my $x" as argument.
  Fixes op/index.t test 122.

Generated with [Devin](https://cli.devin.ai/docs)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: fglock

src/main/java/org/perlonjava/backend/bytecode/Opcodes.java

@@ -2066,9 +2066,9 @@ public class Opcodes {
      * Format: CREATE_LAST_DYNAMIC rd labelReg
      * Creates RuntimeControlFlowList with label from registers[labelReg].toString().
      */
-    public static final short CREATE_LAST_DYNAMIC = 413;
-    public static final short CREATE_NEXT_DYNAMIC = 414;
-    public static final short CREATE_REDO_DYNAMIC = 415;
+    public static final short CREATE_LAST_DYNAMIC = 443;
+    public static final short CREATE_NEXT_DYNAMIC = 444;
+    public static final short CREATE_REDO_DYNAMIC = 445;
 
     // ExtendedNativeUtils operators (user/group info, network lookups, enumeration)
     public static final short GETLOGIN = 416;

src/main/java/org/perlonjava/core/Configuration.java

@@ -33,7 +33,7 @@ public final class Configuration {
      * Automatically populated by Gradle/Maven during build.
      * DO NOT EDIT MANUALLY - this value is replaced at build time.
      */
-    public static final String gitCommitId = "b2a0f09c3";
+    public static final String gitCommitId = "509cc4f94";
 
     /**
      * Git commit date of the build (ISO format: YYYY-MM-DD).

src/main/java/org/perlonjava/frontend/parser/PrototypeArgs.java

@@ -89,25 +89,23 @@ private static boolean allowsZeroArguments(String prototype) {
         }
 
         char firstChar = prototype.charAt(i);
-        return firstChar == ';' || firstChar == '@' || firstChar == '%';
+        return firstChar == ';' || firstChar == '@' || firstChar == '%' || firstChar == '_';
     }
 
     /**
      * Checks if the prototype represents a named unary operator.
-     * In Perl, functions with prototype ($) or (_) are parsed as named unary
+     * In Perl, functions with exactly prototype ($) or (_) are parsed as named unary
      * operators with higher precedence than comparison operators.
+     * Prototypes like ($;), (_;), ($;$) are NOT named unary - the trailing semicolon
+     * makes them list operators.
      *
      * @param prototype The prototype string
-     * @return true if the prototype is a single-scalar named unary pattern
+     * @return true if the prototype is exactly "$" or "_"
      */
     private static boolean isNamedUnaryPrototype(String prototype) {
-        if (prototype.isEmpty()) return false;
+        if (prototype.length() != 1) return false;
         char first = prototype.charAt(0);
-        if (first != '$' && first != '_') return false;
-        // Exactly one character: "$" or "_"
-        if (prototype.length() == 1) return true;
-        // Optional args follow: "$;..." or "_;..."
-        return prototype.charAt(1) == ';';
+        return first == '$' || first == '_';
     }
 
     /**
@@ -168,6 +166,13 @@ static ListNode consumeArgsWithPrototype(Parser parser, String prototype, boolea
                 if (!allowsZeroArguments(prototype)) {
                     throwNotEnoughArgumentsError(parser);
                 }
+                // _ prototype defaults to $_ when no argument is provided
+                if (prototype.charAt(0) == '_') {
+                    Node underscoreArg = new OperatorNode(
+                            "$", new IdentifierNode("_", parser.tokenIndex), parser.tokenIndex);
+                    underscoreArg.setAnnotation("context", "SCALAR");
+                    args.elements.add(underscoreArg);
+                }
                 return args;
             }
             // Parse one argument at named unary precedence (higher than comparison ops)

src/main/java/org/perlonjava/frontend/parser/SignatureParser.java

@@ -339,9 +339,10 @@ private Node parseDefaultValue(Node paramVariable) {
             return null;
         }
 
-        // Parse the default value expression
-        ListNode arguments = consumeArgsWithPrototype(parser, "$", false);
-        return arguments.elements.getFirst();
+        // Parse the default value expression at comma precedence, so that
+        // complex expressions (ternary, comparisons, logical ops) are included
+        // but ',' and ')' correctly terminate the default value.
+        return parser.parseExpression(parser.getPrecedence(","));
     }
 
     /**

src/main/java/org/perlonjava/runtime/perlmodule/Utf8.java

@@ -39,7 +39,7 @@ public static void initialize() {
         try {
             utf8.registerMethod("import", "useUtf8", ";$");
             utf8.registerMethod("unimport", "noUtf8", ";$");
-            utf8.registerMethod("upgrade", "$");
+            utf8.registerMethod("upgrade", null);
             utf8.registerMethod("downgrade", "$;$");
             utf8.registerMethod("encode", "$");
             utf8.registerMethod("decode", "$");