my @array = ( ... );
  my @adj_diff;
  for ( my $i = 0; $i < $#array; ++$i )
  {
      push @adj_diff, $array[$i+1] - $array[$i];
  }

##</code><code>##

  my @adj_diff = map { $array[$_+1] - $array[$_] } 0 .. $#array-1;