One need to apply this only before 4_03, it is included into 4_03.

--- perl5.004_01.latest/sv.c	Mon Jun 16 11:17:08 1997
+++ perl5.004_01.malloc/sv.c	Sat Jun 28 23:30:14 1997
@@ -4625,7 +4633,7 @@ sv_vcatpvfn(sv, pat, patlen, args, svarg
 	need = (have > width ? have : width);
 	gap = need - have;
 
-	SvGROW(sv, SvLEN(sv) + need);
+	SvGROW(sv, SvCUR(sv) + need + 1);
 	p = SvEND(sv);
 	if (esignlen && fill == '0') {
 	    for (i = 0; i < esignlen; i++)
