Perl call graph polluted by false-positive CALLS edges (builtins, framework method calls, config strings) #476

Summary

On real-world Perl codebases, the call graph is dominated by false-positive CALLS edges. Perl files are extracted (call sites emitted), and any call the textual resolver can't place falls back to a generic short-name matcher that has no language or call-kind awareness. It happily wires Perl builtins, framework method calls, and even mis-parsed config strings to unrelated project subs that merely share a name.

Evidence

Measured on a large real Perl monorepo (~1,200 .pm/.pl + 352 .cgi endpoint files). For .cgi callers, the generic resolver produced 4,940 suffix_match edges, of which the overwhelming majority are noise:

These targets are not project calls at all — the classes belong to CPAN/framework modules not in the graph, the builtins are language primitives, and the config string is a literal. The generic resolver fabricates edges purely on short-name collision.

Root causes

1. Callee over-extraction (Perl): extract_scripting_callee (internal/cbm/extract_calls.c, CBM_LANG_PERL branch) returns the raw first-child text of a call node, so non-identifier tokens (dotted config strings, literals) become callees.
2. No builtin guard: the generic resolver (src/pipeline/registry.c) matches builtin-named calls (shift/push/…) to project subs of the same name.
3. No function-vs-method distinction: CBMCall carries no call-kind, so a method call $obj->commit() with an unknown receiver is treated as a bare function and short-name-matched to a project commit sub.

Proposed fix (language-gated; non-Perl behavior unchanged)

1. Extraction hygiene: in the Perl callee path, extract the real method/function name token and reject non-identifier callees (containing ., quotes, whitespace, etc.) so config strings/literals never become call targets.
2. Builtin guard: add a Perl builtin set; when an unresolved Perl call's name is a builtin, suppress the generic edge (real same-file subs are already resolved by earlier stages before the generic fallback).
3. Method-vs-function: add a is_method flag to CBMCall, set it during Perl extraction for arrow/method calls, thread it into the resolver, and suppress generic short-name matching for Perl method calls with an unknown receiver (precise method resolution is the LSP's job; bare short-name matching is almost always wrong).

Every change is gated on CBM_LANG_PERL — the generic resolver and CBMCall are shared by all languages, so the other nine families remain byte-identical.

Acceptance criteria

• A Perl builtin call (e.g. push @x, 1) does not produce a CALLS edge to a project sub named push.
• A Perl method call with an unknown receiver (e.g. $dbh->commit()) does not generic-match to a project sub named commit.
• A dotted config-string token (e.g. log4perl.appender.File.utf8) is not extracted as a call target.
• Genuine intra-project Perl function calls still resolve.
• Non-Perl languages' extraction/resolution are unchanged (verified by the existing suite + the cross-language breadth check).
• Tests cover all of the above.

Validation (on the proposed branch)

Re-indexing the same repo with the fix: .cgi suffix_match drops 4,940 → 655 (−87%), builtin/CPAN-method/config-string noise on .cgi goes to zero, project-wide CALLS edges drop by ~13,400 (noise removal — fewer, more-correct edges), scripts/build.sh/scripts/test.sh stay green, and the cross-language breadth check confirms all other languages still resolve.