Programming Perl, 4th Edition

strict “vars”

Under this stricture, a compile-time error is triggered if you try to access a variable that hasn’t met at least one of the following criteria:

• Predefined by Perl itself, such as @ARGV, %ENV, and global punctuation variables like $. or $_.

• Declared with our (for a global) or my or state (for a lexical).

• Imported from another package. (The vars pragma fakes up an import, but use our instead.)

• Fully qualified using its package name and the double-colon package separator.

The local operator by itself isn’t good enough to keep use strict "vars" happy because, despite its name, that operator doesn’t change whether the named variable is globally visible. Instead, it gives the variable (or individual element of an array or hash) a new, temporary value for the duration of the block at runtime. You still need to use our to declare a global variable, or my or state to declare a lexical variable. You can, however, localize an our:

local our $law = "martial";

Globals predefined by Perl are exempt from these requirements. This applies to program-wide globals (those forced into package main like @ARGV or $_) and to per-package variables like $a and $b, which are normally used by the sort function. Per-package variables used by modules like Exporter must still be declared using our:

our @EXPORT_OK = qw(name rank serno);