string assignment can sometimes reuse old string alocated memory

src/basic/basic_commands/helper_let_strdesccpy_38K.s

@@ -0,0 +1,32 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Helper routine to copy string descriptor, for LET command
+//
+
+
+#if CONFIG_MEMORY_MODEL_38K
+
+helper_let_strdesccpy:
+
+	ldy #$02
+	lda (VARPNT), y
+	sta DSCPNT+2
+	dey
+	lda (VARPNT), y
+	sta DSCPNT+1
+	dey
+
+	// .Y is now 0 - copy the content
+!:
+	lda (__FAC1+1),y
+	sta (DSCPNT+1),y
+	iny
+	cpy __FAC1+0
+	bne !-
+
+	rts
+
+#endif