More efficient dereferencing of a subroutine return

[gg48gg]

I am inquiring to see if there is a more efficient way, than the below code, to dereference a reference returned from a subroutine. Could you please help me out?

my $temp_scalar=subroutine();
my @ARRAY=@$temp_scalar;
undef $temp_scalar;

sub subroutine {
 my @array=("one", "two"," three");
 return \@array;
}

[tobyink]

my @ARRAY = @{ subroutine() };

This is fewer lines of course, and arguably a bit neater than a temporary variable, but in terms of real efficiency (i.e. CPU, memory, etc) makes very little difference.

[parv]

Darn thing causes fatal error of Can't use an undefined value as an ARRAY reference if undef is received under strict 'refs', where the dereference result could have been an empty list without the need to invoke no strict .... I will take the temporary variable to do a check first.

[frozenwithjoy]

Can you show what exactly gives you that error? I get no errors/warnings with this:

#!/usr/bin/env perl
use strict;
use warnings;
use feature 'say';

my @result = @{ subroutine() };
say "@result";

sub subroutine {
    my @array = ();
    return \@array;
}

[tobyink]

In that case,

my @ARRAY = @{ subroutine() || [] };

[Anonymous Monk]

what? Can you demonstrate that?

[mrbark]

If the dereferencing of an array returned by a function is my $arrayref = \@{ function() } then how does that work with the keys() function?

I tried my $arrayref = \@{ keys(%$someHashRef) || [] } but something makes it break.

What makes the keys() function a special case?

[choroba]

You say "dereferencing", but at the same time "$arrayref". That's confusing.

To dereference an array reference returned from a subroutine, you can use:

my @array = @{ sub_returning_aref() };

To get the actual reference, no dereferencing is needed:

my $aref = sub_returning_aref();

On the other hand, if a subroutine returns a list, you can assign it directly to an array:

my @array = sub_returning_list();

To create an array reference, you need to create an anonymous array, as the subroutine returns a list, not an array.

my $aref = [ sub_returning_list() ];

There's nothing special about keys.

my @array = keys %hash;
my $aref  = [ keys %hash ];

[gg48gg]

Thanks to everyone for your input. For my purposes, I don't have to worry about the possibility of my sub returning undef. So, I like tobyink's:

my @ARRAY = @{ subroutine() };

for it's simplicity and function. I will keep in mind Anon's recommendation for using 'eval' in the event I need to handle possibility of undef. Thanks all! I hope this thread is useful for others in the future. I didn't find what I was looking for when I searched. Cheers.

[gg48gg]

Hey all. Related question. Is there a way to avoid this multi step operation when I have multiple return values of a sub? e.g.:

my ($ref1, $ref2) = retarrayrefs();
my @arr1=@$ref1;
my @arr2=@$ref2;

sub retarrayrefs {
 my @arr1=qw(one two three);
 my @arr2=qw(four five six seven);
 return (\@arr1,\@arr2);
}

I was trying many variations of the below, but none work properly, and it just doesn't seem like a good thing to do. Should I stop trying to shorten this code and simply stick with the above?

my (@arr1,@arr2) = ( ${retarrays()[0]}, ${retarrays()[1]} );

[LanX]

Are you aware that Perl has list-context?

my @ARRAY=subroutine();

sub subroutine {
 my @array=("one", "two"," three");
 return @array;
}

If you still need to return an array-ref in other cases just check wantarray in a condition to see if a scalar is expected.

return wantarray ? @array : \@array;

[bulk88]

Don't make a copy of the array to another array. no "my @ARRAY=@$temp_scalar;" just do $temp_scalar->[5].