our @foo = ( 0 );
my  @bar = ( 'a' );
{
  local @foo = ( 1 );
  my    @bar = ( 'b' );
  baz();
  print "$foo[ 0 ] $bar[ 0 ]\n"; # may not print "1 b"
}

sub baz {
  $foo[ 0 ] = 3;
  $bar[ 0 ] = 'x';
}
__END__
3 b