What does the 'Array => [...]' notation mean

Question

In some Perl code I have been asked to maintain, I encountered the following construct:

myArray => ['id1', 'id2', 'id3', 'id4']

I searched the web for some definition/explanation of this but all I could find was a reference to scalar hashing:

This is a snippet from the actual code I encountered:

$config = eval {
    XMLin(
        $inFile,
        MyArray => [
            'id1', 'id2',"id3", 'id4'
        ]
    );
};

What does that syntax of hashing an entire array (without the hash values) mean?

duplicate https://stackoverflow.com/questions/4093895/how-does-double-arrow-operator-work-in-perl but welcome to SO — KeepCalmAndCarryOn, Jul 07 '19 at 10:32
@KeepCalmAndCarryOn Thank you. I will check that link that you provided (I did search SO before I posted but couldn't find it). Maybe this is not an exact duplicate because I was referring to this confusing array declaration onlly. — datsb, Jul 07 '19 at 10:38
The `[ ]` brackets create an array ref: https://stackoverflow.com/a/50155543/14955 — Thilo, Jul 07 '19 at 10:44
What do you mean by "hashing an entire array without the hash values"? The array is the value. — melpomene, Jul 07 '19 at 10:46
By the way, you should avoid XML::Simple. Despite its name, [it's so complicated to use](https://stackoverflow.com/q/33267765/589924) that its own documentation recommends avoiding it. — ikegami, Jul 07 '19 at 11:59

ikegami · Accepted Answer · 2019-07-07T10:55:46.827

You mention hashing and hashes, but neither are involved.

IDENT => ...

is the same as

'IDENT', ...

[ ... ]

is basically equivalent to

do { my @anon = ( ... ); \@anon }

except without the new scope.

XMLin(
    $inFile,
    MyArray => [
        'id1', 'id2',"id3", 'id4'
    ]
);

is equivalent to

my @anon = ( 'id1', 'id2', 'id3', 'id4' );
XMLin($inFile, 'MyArray', \@anon);

This isn't a proper call to XMLin. If present, the second argument should be the name of one of the options (e.g. ForceArray.)

1 Answers1