Fix line editing and loadmod error checking

src/a1cmd.pla

@@ -511,13 +511,13 @@ def rdstr(prompt)
     repeat
         ch = cin
 	when ch
-	    is $08 ; right arrow
+	    is $15 ; right arrow
 	        if inbuff.0 < maxlen
 		    inbuff.0 = inbuff.0 + 1
 		    ch = inbuff[inbuff.0]
 		    cout(ch)
 		fin
-	    is $15 ; left arrow
+	    is $08 ; left arrow
 	        if inbuff.0
 		    cout('\\')
 		    cout(inbuff[inbuff.0])
@@ -709,6 +709,9 @@ def loadmod(mod)
     ;
     dcitos(mod, @filename)    
     rdlen = (finddirentry(@filename)):$15
+    if perr
+        return -perr
+    fin
     if rdlen > 0
         readfile(@filename, heap)
 	modsize = (heap):0