$b = '           fred and bill        ';;

Dump $b;;
SV = PV(0x13be50) at 0x13e0d8
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x1b3558 "           fred and bill        "\0
  CUR = 32
  LEN = 40

$b =~ s[^\s*(.*?)\s*$][$1];;
Dump $b;;
SV = PVMG(0x207928) at 0x13e0d8
  REFCNT = 1
  FLAGS = (SMG,POK,pPOK)
  IV = 0
  NV = 0
  PV = 0x38b4388 "fred and bill"\0
  CUR = 13
  LEN = 16
  MAGIC = 0x391bda8
    MG_VIRTUAL = &PL_vtbl_mglob
    MG_TYPE = PERL_MAGIC_regex_global(g)
    MG_LEN = -1