man vars () - Perl pragma to predeclare global variable names (obsolete)
NAME
vars - Perl pragma to predeclare global variable names (obsolete)
SYNOPSIS
use vars qw($frob @mung %seen);
DESCRIPTION
NOTE: For variables in the current package, the functionality provided by this pragma has been superseded by CWour declarations, available in Perl v5.6.0 or later. See our in perlfunc.
This will predeclare all the variables whose names are in the list, allowing you to use them under use strict, and disabling any typo warnings.
Unlike pragmas that affect the CW$^H hints variable, the CWuse vars and CWuse subs declarations are not BLOCK-scoped. They are thus effective for the entire file in which they appear. You may not rescind such declarations with CWno vars or CWno subs.
Packages such as the AutoLoader and SelfLoader that delay loading of subroutines within packages can create problems with package lexicals defined using CWmy(). While the vars pragma cannot duplicate the effect of package lexicals (total transparency outside of the package), it can act as an acceptable substitute by pre-declaring global symbols, ensuring their availability to the later-loaded routines.
See Pragmatic Modules in perlmodlib.