#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use Readonly;
Readonly my @arr => qw( a b c );

say "@arr";
eval { $arr[1] = 'B' };
say "@arr";
eval { splice @arr, 1, 1, 'C' };
say "@arr";

__END__
Output:
a b c
a b c
a b c