Is returning a whole array from a Perl subroutine inefficient?

Question

I often have a subroutine in Perl that fills an array with some information. Since I'm also used to hacking in C++, I find myself often do it like this in Perl, using references:

my @array;
getInfo(\@array);

sub getInfo {
   my ($arrayRef) = @_;
   push @$arrayRef, "obama";
   # ...
}

instead of the more straightforward version:

my @array = getInfo();

sub getInfo {
   my @array;
   push @array, "obama";
   # ...
   return @array;
}

The reason, of course, is that I don't want the array to be created locally in the subroutine and then copied on return.

Is that right? Or does Perl optimize that away anyway?

Answer 1

What about returning an array reference in the first place?

sub getInfo {
  my $array_ref = [];
  push @$array_ref, 'foo';
  # ...
  return $array_ref;
}

my $a_ref = getInfo();
# or if you want the array expanded
my @array = @{getInfo()};

Edit according to dehmann's comment:

It's also possible to use a normal array in the function and return a reference to it.

sub getInfo {
  my @array;
  push @array, 'foo';
  # ...
  return \@array;
}      

Answer 2

Passing references is more efficient, but the difference is not as big as in C++. The argument values themselves (that means: the values in the array) are always passed by reference anyway (returned values are copied though).

Question is: does it matter? Most of the time, it doesn't. If you're returning 5 elements, don't bother about it. If you're returning/passing 100'000 elements, use references. Only optimize it if it's a bottleneck.