I agree on a warning, it would be a practical thing, after all. And after that, a real fix with 'die' a couple versions later should help the legacy code.
Well anyway, I found the code suggested by ikegami, so would you guys review the patch please?
--- pp.c.0 2012-01-06 01:07:34.511988700 +0100
+++ pp.c 2012-01-06 19:04:06.311428300 +0100
@@ -515,9 +515,11 @@
SvTEMP_off(sv);
SvREFCNT_inc_void_NN(sv);
}
- else if (SvPADTMP(sv) && !IS_PADGV(sv))
+ else if (SvPADTMP(sv) && !IS_PADGV(sv)) {
+ Perl_ck_warner(aTHX_ packWARN(WARN_MISC),
+ "Implicit copy of a read-only scalar due to aliasing");
sv = newSVsv(sv);
- else {
+ } else {
SvTEMP_off(sv);
SvREFCNT_inc_void_NN(sv);
}