How can I resolve the warning "Use of assignment to $[ is deprecated"?

Question

I have a program that I downloaded from an older computer to a newer one. It has the following snippet of code:

#!/bin/perl -w

use strict;

$[ = 1;    # set array base to 1
$, = ' ';    # set output field separator
$\ = "\n";    # set output record separator

However, when I try to run the script I get the following error message:

Use of assignment to $[ is deprecated at ./test.pl line 5.

Any idea on how to resolve this?

I am using the following version of perl:

This is perl 5, version 16, subversion 3 (v5.16.3) built for x86_64-linux-thread-multi

Answer 1

The use of $[ has been discouraged, deprecated, and all but disallowed. See it in perlvar (it is in Deprecated and Removed Variables section^†) and see the core arybase where it's been moved.

Still, if you must, you can disable this particular warning category   (Update: only in pre-v5.30)^†

use strict;
use warnings;

# Restrict the scope as much as possible
{ 
    no warnings 'deprecated';
    $[ = 1;                               # NOT possible in v5.30+
    
    # ...
}

Now it will not print that warning, and it will work since it is still legal. (Not in v5.30+) ^†

Note that this also changes other offsets, for strings for example, but not yet some others. It is a very, very old "feature," please read the documentation.

I'd strongly recommend rewriting the script, if at all possible.

---

^†  Still the same status in v5.30   ... but:   "Assigning non-zero to $[ is no longer possible".

Thus you cannot anymore assign, regardless of warnings or errors (those can be suppressed or handled). Then either rewrite the script or use Array::Base if you must work with that offset, as in mob's answer

Answer 2

The module Array::Base implements the array index offset feature in modern versions of perl. For a self-constrained script, beginning the script with

use Array::Base (1);

should behave pretty similarly to an older script that says

$[ = 1;

at the top, but see the docs for some potentially important disclaimers.