$rec->vals we can presume is some OO code, but's it's not defined by the OP.

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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