#!/usr/local/bin/perl
use strict;
use warnings;
{
  package _;
  use Carp;
  sub TIESCALAR { bless {}, shift }
  no warnings 'once';
  sub FETCH { croak q(Don't you dare get $_)  }
  sub STORE { croak q(Don't you dare set $_)  }
}
tie $_, "_";
my @a = (0..9);
my @b = map  { $_ * $_ } @a;
my @c = grep { $_ % 2  } @b;
local $\ = "\n"; # make print say
print for @c;
print while (<DATA>)
__DATA__
one
two
three