@array = ('a');
foreach (@array) {
   # $_ is an alias for $array[0].
   {
      local $_;  # This $_ is not an alias for $array[0].
      while (<DATA>) { }
   }
   # Neither $_ nor $array[0] are clobbered
   print("[$_]$/");      # Prints "[a]"
}
print("[$array[0]]$/");  # Prints "[a]"