arybase3perl

Usage

    $[ = 1;
    @a = qw(Sun Mon Tue Wed Thu Fri Sat);
    print $a[3], "\n";  # prints Tue

Overview

This module implements Perl's $[ variable. You should not use it directly.

Assigning to $[ has the compile-time effect of making the assigned value, converted to an integer, the index of the first element in an array and the first character in a substring, within the enclosing lexical scope.

It can be written with or without "local":

    $[ = 1;
    local $[ = 1;

It only works if the assignment can be detected at compile time and the value assigned is constant.

It affects the following operations:

    $array[$element]
    @array[@slice]
    $#array
    (list())[$slice]
    splice @array, $index, ...
    each @array
    keys @array
    index $string, $substring  # return value is affected
    pos $string
    substr $string, $offset, ...

As with the default base of 0, negative bases count from the end of the array or string, starting with -1. If $[ is a positive integer, indices from "$[-1" to 0 also count from the end. If $[ is negative (why would you do that, though?), indices from $[ to 0 count from the beginning of the string, but indices below $[ count from the end of the string as though the base were 0.

Prior to Perl 5.16, indices from 0 to "$[-1" inclusive, for positive values of $[, behaved differently for different operations; negative indices equal to or greater than a negative $[ likewise behaved inconsistently.