DB<55> @R= map { \$_ } $a

  DB<56> x @R
0  REF(0x31fae58)          # 
   -> ARRAY(0x3353230)
           empty array
  DB<57> x \$a
0  REF(0x31fae58)          # same
   -> ARRAY(0x3353230)
           empty array
  DB<58> $b=$a

  DB<59> x \$b 
0  REF(0x3353a58)          # different
   -> ARRAY(0x3353230)
           empty array
  DB<60>