$ perl -MDevel::Peek -le'utf8::upgrade(my $x = chr(0xE9)); print length($x); Dump($x)'
1
SV = PVMG(0x817fd40) at 0x814cc6c
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,SMG,POK,pPOK,UTF8)
  IV = 0
  NV = 0
  PV = 0x815bda0 "\303\251"\0 [UTF8 "\x{e9}"]
  CUR = 2
  LEN = 3
  MAGIC = 0x8163060
    MG_VIRTUAL = &PL_vtbl_utf8
    MG_TYPE = PERL_MAGIC_utf8(w)
    MG_LEN = 1
$ perl -MDevel::Peek -le'utf8::encode(my $x = chr(0xE9)); print length($x); Dump($x)'
2
SV = PV(0x814ce90) at 0x814cc6c
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  PV = 0x815bda0 "\303\251"\0
  CUR = 2
  LEN = 3