How to reference a split expression in Perl?

Question

I want to create a reference to an array obtained by a split in Perl. I'm thinking something like:

my $test = \split( /,/, 'a,b,c,d,e');

foreach $k (@$test) {
   print "k is $k\n";
}

But that complains with Not an ARRAY reference at c:\temp\test.pl line 3. I tried a few other alternatives, all without success.

Answer 1

Background explanation:

split, like other functions, returns a list. You cannot take a reference to a list. However, if you apply the reference operator to a list, it gets applied to all its members. For example:

use Data::Dumper;

my @x = \('a' .. 'c');

print Dumper \@x

Output:

$VAR1 = [
          \'a',
          \'b',
          \'c'
        ];

Therefore, when you write my $test = \split( /,/, 'a,b,c,d,e');, you get a reference to the last element of the returned list (see, for example, What’s the difference between a list and an array?). Your situation is similar to:

Although it looks like you have a list on the righthand side, Perl actually sees a bunch of scalars separated by a comma:

my $scalar = ( 'dog', 'cat', 'bird' );  # $scalar gets bird

Since you’re assigning to a scalar, the righthand side is in scalar context. The comma operator (yes, it’s an operator!) in scalar context evaluates its lefthand side, throws away the result, and evaluates it’s righthand side and returns the result. In effect, that list-lookalike assigns to $scalar it’s rightmost value. Many people mess this up becuase they choose a list-lookalike whose last element is also the count they expect:

my $scalar = ( 1, 2, 3 );  # $scalar gets 3, accidentally

In your case, what you get on the RHS is a list of references to the elements of the list returned by split, and the last element of that list ends up in $test. You first need to construct an array from those return values and take a reference to that. You can make that a single statement by forming an anonymous array and storing the reference to that in $test:

my $test = [ split( /,/, 'a,b,c,d,e') ];