fix(pack): byte-counted slash construct must not re-encode as UTF-8

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

@@ -33,22 +33,22 @@ 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 = "d5085fda8";
+    public static final String gitCommitId = "723dfee80";
 
     /**
      * Git commit date of the build (ISO format: YYYY-MM-DD).
      * Automatically populated by Gradle/Maven during build.
      * DO NOT EDIT MANUALLY - this value is replaced at build time.
      */
-    public static final String gitCommitDate = "2026-04-29";
+    public static final String gitCommitDate = "2026-04-30";
 
     /**
      * Build timestamp in Perl 5 "Compiled at" format (e.g., "Apr  7 2026 11:20:00").
      * Automatically populated by Gradle during build.
      * 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 30 2026 08:15:13";
+    public static final String buildTimestamp = "Apr 30 2026 10:12:03";
 
     // Prevent instantiation
     private Configuration() {

src/main/java/org/perlonjava/runtime/operators/pack/PackGroupHandler.java

@@ -340,10 +340,14 @@ public static GroupResult handleSlashConstruct(String template, int position, in
             if (stringCount >= 0) {
                 effectiveCount = stringCount;
             } else {
-                byte[] strBytes = byteMode
-                        ? str.getBytes(StandardCharsets.ISO_8859_1)
-                        : str.getBytes(StandardCharsets.UTF_8);
-                effectiveCount = strBytes.length;
+                // Match the byte/char count used by PackWriter.writeString:
+                // - byte mode (U0): raw bytes via ISO-8859-1
+                // - normal mode: one unit per Java character (writeString writes
+                //   one byte per ISO-8859-1 char, or one codepoint for high Unicode)
+                int unitCount = byteMode
+                        ? str.getBytes(StandardCharsets.ISO_8859_1).length
+                        : str.length();
+                effectiveCount = unitCount;
                 if (stringFormat == 'Z') {
                     effectiveCount++; // Include null terminator in count
                 }

src/test/resources/unit/pack/slash_string.t

@@ -0,0 +1,59 @@
+#!/usr/bin/perl
+use strict;
+use warnings;
+use Test::More tests => 7;
+
+# Tests for the "len/Z*" / "len/a*" / "len/A*" pack constructs with byte
+# strings (Latin-1 high bytes). Regression for a bug where the slash
+# construct used getBytes(UTF-8) to compute the length prefix while
+# writeString() emitted ISO-8859-1 bytes, producing a wrong (doubled)
+# length and trailing zero padding. This is what BSON::PP triggers via
+# pack("V/Z*", $utf8_encoded_string).
+
+my $latin = "\xc3\xa9\xc3\xa9\xc3\xa9";   # 6 bytes, no utf8 flag
+
+is(
+    unpack("H*", pack("V/Z*", $latin)),
+    "07000000c3a9c3a9c3a900",
+    'V/Z* length prefix counts bytes (not re-encoded UTF-8) for Z*',
+);
+
+is(
+    unpack("H*", pack("V/a*", $latin)),
+    "06000000c3a9c3a9c3a9",
+    'V/a* length prefix counts bytes for a*',
+);
+
+is(
+    unpack("H*", pack("V/A*", $latin)),
+    "06000000c3a9c3a9c3a9",
+    'V/A* length prefix counts bytes for A*',
+);
+
+is(
+    unpack("H*", pack("n/Z*", $latin)),
+    "0007c3a9c3a9c3a900",
+    'n/Z* length prefix counts bytes for Z*',
+);
+
+# Round-trip through unpack
+{
+    my $p = pack("V/a*", $latin);
+    my ($got) = unpack("V/a*", $p);
+    is($got, $latin, 'V/a* round-trips a Latin-1 byte string');
+}
+
+# Mirror BSON::PP's exact use: a 0x02 (string) field in a tiny BSON doc.
+# Field value is "ééééée" already utf8-encoded to 12 bytes. The BSON
+# string framing should report length=13 (12 bytes + NUL) and emit
+# exactly 13 bytes of payload.
+{
+    my $v = "\xc3\xa9" x 6;             # 12 bytes, utf8 flag off
+    my $p = pack("V/Z*", $v);
+    is(length($p), 4 + 13, 'V/Z* total length is 4 (len prefix) + bytes + NUL');
+    is(
+        unpack("H*", $p),
+        "0d000000" . ("c3a9" x 6) . "00",
+        'V/Z* matches BSON wire format',
+    );
+}