Is there a difference between Perl's shift versus assignment from @_ for subroutine parameters?

Question

Let us ignore for a moment Damian Conway's best practice of no more than three positional parameters for any given subroutine. Is there any difference between the two examples below in regards to performance or functionality? Using `shift`: ``` sub do_something_fantastical { my $foo = shift; my $bar = shift; my $baz = shift; my $qux = shift; my $quux = shift; my $corge = shift; } ``` Using `@_`: ``` sub do_something_fantastical { my ($foo, $bar, $baz, $qux, $quux, $corge) = @_; } ``` Provided that both examples are the same in terms of performance and functionality, what do people think about one format over the other? Obviously the example using `@_` is fewer lines of code, but isn't it more legible to use `shift` as shown in the other example? Opinions with good reasoning are welcome.

Accepted Answer

There's a functional difference. The shift modifies `@_`, and the assignment from `@_` does not. If you don't need to use `@_` afterward, that difference probably doesn't matter to you. I try to always use the list assignment, but I sometimes use `shift`.

However, if I start off with `shift`, like so:

```
 my( $param ) = shift;
```

I often create this bug:

```
 my( $param, $other_param ) = shift;
```

That's because I don't use `shift` that often, so I forget to get over to the right hand side of the assignment to change that to `@_`. That's the point of the best practice in not using `shift`. I could make separate lines for each `shift` as you did in your example, but that's just tedious.

Is there a difference between Perl's shift versus assignment from @_ for subroutine parameters?

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