fix(parser): do not consume keywords across whitespace in qualified names

[fglock]

Summary

Fixes a parser bug where %Foo:: and 2 (and similar) was rejected with a syntax error.

In real perl, qualified identifiers cannot contain whitespace around the :: separator. So:

• %Foo:: and 2 → stash hash %Foo:: followed by the low-precedence operator and
• %Foo::and → hash named "and" in package Foo (no space, single identifier)

PerlOnJava's IdentifierParser.parseComplexIdentifierInner was calling Whitespace.skipWhitespace immediately after consuming :: (and the legacy ' separator), which caused it to greedily pull the next keyword across the whitespace into the qualified name. So %Foo:: and 2 was parsed as %Foo::and 2 and rejected.

Why this matters

The bundled src/main/perl/lib/Dumpvalue.pm line 110 contains:

and %overload:: and defined &{'overload::StrVal'};

so any code path that loads Dumpvalue died at compile time. CPAN.pm lazily requires Dumpvalue from its error/dump handler, so the user-visible symptom was that running e.g.

$ ./jcpan -t JSON::Literal

died with syntax error at jar:PERL5LIB/Dumpvalue.pm line 110, near "&" instead of the actual CPAN diagnostic. Reduced repro:

$ ./jperl -e '%foo:: and 2 ; print "ok\n"'   # syntax error  (before)
$ perl     -e '%foo:: and 2 ; print "ok\n"'  # ok

Fix

Stop skipping whitespace after :: and ' in parseComplexIdentifierInner. The next token must be flush against the separator to be treated as a continuation of the qualified name. Keywords (and, or, etc.) are still allowed inside qualified names when there's no whitespace, e.g. $Foo::and, &UNIVERSAL::isa.

Test plan

• New unit test src/test/resources/unit/stash_var_keyword_op.t covers:
  • %Foo:: and 1, %Foo:: or ..., %Foo:: xor 0, 1 and %Foo:: and 2
  • not %Foo::, 1 and %Foo:: (trailing stash with no operator)
  • %Foo:: && 1 (high-precedence form, regression check — was already OK)
  • keys %Foo::, scalar(keys %Foo::) cmp 0
  • %Foo::and (no space) still resolves to the hash named "and" in Foo
  • $Foo::or (no space) still resolves to the scalar named "or" in Foo
  • The exact Dumpvalue.pm line 110 pattern (and %overload:: and defined ...) compiles
• Test fails on master, passes on this branch
• make (full unit test suite) passes
• ./jperl -e 'use Dumpvalue; print "ok\n"' now succeeds

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