What Fletch is doing here is testing the value returned by $rec->val, and according to the result, returning a reference to one of the two arrays. This whole things is wrapped in a @{ } which will deference the array ref returned in the first instance, which he can then push the value to.

Here's a slightly less complicated version, using the same principal

use strict;
use Data::Dumper;

my @numbers = (1,2,3,45,6,76,8,5,7,8);
my(@odd, @even);

foreach my $number (@numbers) {
    push @{ is_odd($number) ? \@odd : \@even}, $number;
}

print Dumper(\@odd, \@even);

sub is_odd {$_[0] % 2}
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Could you explain what does it mean @{$rec->vals}.

@{$rec->vals}
can be written as
@{$rec->vals()}
or as
my $aref = $rec->vals();
@{$aref}

Is it array ref?

$rec->vals() is an expression that returns an array reference.
@{$rec->vals()} is an expression that returns an array lvalue (which means it can be used like a real array).

Update: Fixed problem noted by merlyn.

@{$rec->vals()} is an expression that returns a list.

Well, technically, it's an lvalue array expression, which when used as an rvalue in a list context, returns a list. When its used in a scalar context, it returns the length of the list. When it's used as an lvalue, it's an array.

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

Can you back that up? I can't find any way of using it as an lvalue. Everything I tried gave me a count (in scalar context) or a list (in list context). Some tests:

Read more... (2 kB)

Are you talking about guts? I don't know anything about those. I was talking about the language.