exists(
  deref(
    deref(
      $hashRef,
      "key1"
    ),
    "key2"
  )
)

##</code><code>##

$state = 1;

sub retrieve_a_value {
  # a subroutine that just... does some things
  # and one of those things involves a state change:
  $success = Resource::External::retrieve();
  $state = 2 if $success;
  return $success;
}    

sub mess_it_all_up {
  if( $state == 1 && retrieve_a_value) {
    $_[0] = 1;
  }
  else {
    return $_[0];
  }
}

if ( mess_it_all_up($hashRef->{key1}->{key2}) ) {
  ...
}
else {
  die "Whoah. I couldn't mess it all up at this point even though I should be able to.";
}