need an explanation

[Lennotoecom]

Hi, can you explain please
how exactly this snippet works,
and if possible context transformation:

@a = qw(a b c d e);
$b = () = @a;  # $b now is 5

Thanks!

update:
$b = @a;
would do the same effect,
so basically there is no need for ();
but still, the question remains if someone got
any explanation

update update:
thank you for answer Mr. Choroba
yes indeed that was just the wrong example that was used by some fellow
your last example was helpful
thank a lot

[choroba]

The first line is equivalent to

@a = ('a', 'b', 'c', 'd', 'e');

qw just "quotes words".

The second line is usually written as

$b = @a;

or, for more clarity,

$b = scalar @a;

Perl is sensitive to context. By assigning to a scalar value, you impose the scalar context on the right hand side of the assignment. Arrays return their size (number of elements) in scalar context. Using = () = here has no effect and is only confusing. Update: It is usually used to force list context, for example

$x = () = "abcdABCabA" =~ /a/ig; # Count A's regardless of case.