$ perl
@foo = 1..5;
$" = ':';

{
  # setup
  *bar = \@foo; # or other aliasing method, or localise from foo itself
  local @bar[3..$#bar];
  splice @bar, 3;

  # "test" code
  print "[1] =@bar=\n";
  splice @bar, 1, 0, 'new';
  print "[2] =@bar=\n";
}

# examine @foo after
print "[3] =@foo=\n";
^D
[1] =1:2:3=
[2] =1:new:2:3=
[3] =1:new:2:4:5=