Dereferencing values from an array to declared variables in one line

Question

To retrieve arguments from a function call I usually do

use strict;
use warnings;

foo([1,2],[3,4]);

sub foo{
    my ($x, $y) = @_;
    ...
}

In the example, $x and $y are now references to an array each. If I want to use the variables inside these arrays easily I dereference them first.

...
my ($x1, $x2) = @{$x}[0,1];
# ...same for $y

I'm wondering if there is a way to dereference the arguments in @_ (or, indeed, any other array) and return them to a list of declared variables in just one line?

Answer 1

foo ( [1,2], [3,4] );

sub foo {

    my ( $x1, $x2, $y1, $y2 ) = map @$_, @_;

    ...
}

The map takes @_ and dereferences each of its elements into an array with the @$_ operation.

One could also use List::Gen's deref or d functions to achieve the same goal.

Answer 2

That's why I have unroll:

sub unroll (@) { 
    return map { ref() eq 'ARRAY' ? @$_ : ref() eq 'HASH' ? %$_ : $_ } @_;
}

So that I can go like this:

my ($x1, $y1, $x2, $y2) = unroll @_;

(or)

my ($x1, $y1, $x2, $y2) = &unroll;

A lot prettier than

map { @$_ } @_[0, 1]

and the like. Plus, it's a bit more robust.