$s = 'the quick brown fox';;
$r = \substr $s, 10, 5;;
$$r = 'green';;

print $s;;
the quick green fox

##</code><code>##

$r2 = $r;;
$$r2 = 'orange';;

print $s;;
the quick orange fox

##</code><code>##

print Dump $r2;;

SV = RV(0x186d8d0) at 0x196d088
  REFCNT = 1
  FLAGS = (ROK)
  RV = 0x196d0dc
  SV = PVLV(0x186c9f4) at 0x196d0dc
    REFCNT = 2
    FLAGS = (PADMY,GMG,SMG,pPOK)
    IV = 0
    NV = 0
    PV = 0x19be29c "orange"\0 ######## This seems to be redundant to me.
    CUR = 6
    LEN = 7
    MAGIC = 0x182a75c
      MG_VIRTUAL = &PL_vtbl_substr
      MG_TYPE = PERL_MAGIC_substr(x)
    TYPE = x
    TARGOFF = 10                  ### Offset
    TARGLEN = 5                   ### Length
    TARG = 0x2350bc
    SV = PV(0x2354ac) at 0x2350bc ### The original SV
      REFCNT = 2
      FLAGS = (POK,pPOK)
      PV = 0x182a7bc "the quick orange fox"\0
      CUR = 20
      LEN = 21