add pack("x")

Author: fglock

MILESTONES.md

@@ -314,6 +314,7 @@ The following areas are currently under active development to enhance the functi
 - **v5.42.2**: Next minor version
 
   - Add special variables: `@{^CAPTURE}`, `${^LAST_SUCCESSFUL_PATTERN}`.
+  - Add pack format `x`.
   - Bugfix in regex `/r`.
   - Bugfix in transliterate with octal values.
   - Bugfix in nested heredocs.

src/main/java/org/perlonjava/operators/Pack.java

@@ -113,6 +113,10 @@ public static RuntimeScalar pack(RuntimeList args) {
                 PackHelper.writeUuencodedString(output, str);
             } else if (format == 'a' || format == 'A' || format == 'Z') {
                 valueIndex = handleStringFormat(valueIndex, values, hasStar, format, count, byteMode, output);
+            } else if (format == 'x') {
+                for (int j = 0; j < count; j++) {
+                    output.write(0);
+                }
             } else {
                 // Numeric formats
                 for (int j = 0; j < count; j++) {