fix: List::MoreUtils PP-mode test failures (RC1-RC5)

[fglock]

Summary

Fixes 6 of 7 failing subtests in ./jcpan -t List::MoreUtils (v0.430). The full plan and per-RC rationale live in dev/modules/list_moreutils.md.

	master	this PR
Total subtests	4492	4533
Failing subtests	7 (across 8 files)	1 (in 1 file)
Green test files	53 / 61	60 / 61

The one remaining failure is indexes.t test 18, a Scalar::Util::weaken-on-temporary test (RC6 in the design doc). That sits on top of PerlOnJava's cooperative-refcount overlay and is being addressed on a separate weaken branch; this PR does not touch it.

Commits

Commit	RC	Fixes
db94a5ae1	RC1	strict-refs violation for numeric scalar deref — binsert.t, bremove.t, mesh.t, zip6.t
a161fa284	RC3	POSIX::setlocale / localeconv / LC_* stubs — minmaxstr.t
3bfaffda3	RC2	hoist my in EXPR for LIST; / EXPR while COND; statement-modifier bodies to outer scope — unblocks part.t
c9b8e05dd	RC4	split emits empty field between zero-width and consuming match at the same offset — mode.t
96c4f92d5	RC5	warn Use of uninitialized value in array|hash element on undef subscript — part.t leak-free tests
f67c5860c	docs	record progress in dev/modules/list_moreutils.md

What changed

RC1 — strict-refs for numeric deref (RuntimeScalar.java, RuntimeScalarReadOnly.java)

arrayDeref() / hashDeref() used to silently return empty or throw Not a HASH reference for INTEGER / DOUBLE. They now throw the perl-compatible Can't use string ("N") as an ARRAY\|HASH ref while "strict refs" in use. RuntimeScalarReadOnly picks up the same rule for loop aliases to literals (for my $x (1) { @$x }), but new arrayDerefGet / hashDerefGet overrides keep 1->[0] / 1->{a} silent to match perl's literal-arrow compile-time optimization.

RC3 — POSIX stubs (src/main/perl/lib/POSIX.pm)

POSIX.pm already exported setlocale, localeconv, and the LC_* constants — none of them were actually defined. Added Perl stubs: setlocale returns its locale argument, localeconv returns a default "C"-locale table, LC_* are distinct small integers.

RC2 — my hoisting in statement-modifier loops (StatementResolver.java)

Perl treats my @x = EXPR for LIST; as declaring @x in the enclosing scope (so the rest of the block can refer to it) while each iteration creates a fresh instance. The parser now detects this pattern for for/foreach and while/until modifiers, emits a bare my DECL; before the loop, and wraps the while/until body in a BlockNode so the inner my shadows the outer on each iteration. Outer-scope value matches perl: empty / undef.

RC4 — split with zero-width ∥ consuming alternation (Operator.java)

Java's Matcher always tries alternations left-to-right, so in (?:\b|\s) the \b branch always wins and \s is never attempted at the same offset. Perl's split, in contrast, re-runs the regex with REG_NOTEMPTY_ATSTART after each zero-width match — a consuming alternative at the same position becomes an additional separator with an empty field between the two. After each zero-width match we now probe via Matcher.matches() on progressively larger regions starting at matchEnd; the shortest region the pattern matches gives the length of the consuming alternative.

RC5 — undef-as-subscript warning (RuntimeArray.java, RuntimeHash.java)

RuntimeArray.get / RuntimeHash.get now emit Use of uninitialized value in array\|hash element (category uninitialized) when called with an UNDEF index. Both the read and lvalue/autoviv paths go through get().

Test plan

• make (build + unit tests) green after every commit
• ./jcpan -t List::MoreUtils — 60/61 files green, 1/61 deferred to weaken branch (was 53/61 on master)
• Original 7 failing subtests: 6 now pass, 1 deferred (RC6)
• Hand-verified perl-parity for representative regression cases:
  • use strict; my $x=1; @$x now dies (was silent)
  • print 1->[0] still silent (unchanged)
  • my @x = (1,2) for 1..3; print scalar @x — now prints 0, matching perl
  • split /(?:\b|\s)/, "Lorem ipsum," — matches perl

Generated with Devin

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