fix: preserve string portion of $! for unknown error messages

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 = "121ffb20f";
+    public static final String gitCommitId = "c6eb7bdc7";
 
     /**
      * Git commit date of the build (ISO format: YYYY-MM-DD).
@@ -48,7 +48,7 @@ public final class Configuration {
      * Parsed by App::perlbrew and other tools via: perl -V | grep "Compiled at"
      * DO NOT EDIT MANUALLY - this value is replaced at build time.
      */
-    public static final String buildTimestamp = "Apr 29 2026 20:58:13";
+    public static final String buildTimestamp = "Apr 29 2026 22:10:32";
 
     // Prevent instantiation
     private Configuration() {

src/main/java/org/perlonjava/runtime/runtimetypes/ErrnoVariable.java

@@ -228,13 +228,15 @@ public RuntimeScalar set(String value) {
             int num = Integer.parseInt(value.trim());
             return set(num);
         } catch (NumberFormatException e) {
-            // Not a number and not a known message - store as message with errno 0
-            // Always maintain INTEGER type so numeric operations use the fast path
-            // and never trigger "isn't numeric" warnings via NumberParser.parseNumber()
+            // Not a number and not a known message - store as message with errno 0.
+            // Use DUALVAR so the string portion is preserved when $! is read or
+            // copied (e.g. `my $str = $!`). The numeric side of the dualvar is 0
+            // (a plain INTEGER scalar) so numeric ops don't go through
+            // NumberParser.parseNumber() and won't emit "isn't numeric" warnings.
             this.errno = 0;
             this.message = value;
-            this.type = RuntimeScalarType.INTEGER;
-            this.value = 0;
+            this.type = RuntimeScalarType.DUALVAR;
+            this.value = new DualVar(new RuntimeScalar(0), new RuntimeScalar(value));
             return this;
         }
     }