New deprecation warning: Dot after %s literal is concatenation

1 files changed, 9 insertions, 0 deletions

diff --git a/toke.c b/toke.c
index b5236dadbf..7abcfb756f 100644
--- a/toke.c
+++ b/toke.c
@@ -13117,6 +13117,15 @@ Perl_scan_num(pTHX_ const char *start, YYSTYPE* lvalp)
 		Perl_ck_warner(aTHX_ packWARN(WARN_SYNTAX), "Misplaced _ in number");
 	    }
 
+	    /* Dot here is historically concat, not a radix point.
+	       Deprecate that; it's confusing, and gets in the way of
+	       hex(ish) fractions... but '..' is OK. */
+	    if (s[0] == '.' &&
+		s[1] != '.') {
+		Perl_ck_warner(aTHX_ packWARN(WARN_DEPRECATED),
+			       "Dot after %s literal is concatenation", base);
+	    }
+
 	    sv = newSV(0);
 	    if (overflowed) {
 		if (n > 4294967295.0)