First, I'll note that I don't like our for the simple reason that it makes your package no longer work for older but fairly recent versions of Perl. If there were some significant advantage to its use, then I might start using it anyway. As it stands, I agree with tilly's analysis that our actually offers more disadvantages than advantages.
Moving use strict after your declarations doesn't make any sense to me. The point of use strict it to quickly catch typos in an obvious way so you can immediately fix them rather than spending a lot of time trying to figure out why things aren't working. Well you can still make typos in your standard variable declarations, so why not protect yourself from those?
If you have warnings enabled, then certain typos will be caught for you but a great many others won't. For example, typing $VERSON= 1.01; would generate a warning about a variable being used only once but @VERSION= 1.01; would generate no warning. Writing @EXPORT_OKAY when you meant @EXPORT_OK or @EXPORT_TAG when you mean %EXPORT_TAGS also won't be caught (variables named "VERSION" or /^EXPORT.*/ are exempt from the "used only once" warning).
Even worse, you won't be allowed to use any of the standard variables later in your code. If you decide to include the module version number in an error message or some persistant data or return it to the user, you'll get a fatal error for mentioning $VERSION.
Even if you don't currently use $VERSION in your code, why set yourself up for a maintenance problem down the road? (Or worse, a maintenance problem for the person that inherits your code.)
Is there some advantage to not using strict on your standard variables? I guess it saves you one use vars line (if that, since you will often have to use vars for some "non-standard" package variables anyway). That isn't much savings at all. And I like the use vars line because it means that I'd have to make the same typo at least twice for it to not be caught.
Another place for un-caught typos is @ISA. That is why I'd use base qw( Exporter );. If you mispel "Exporter" in that line, you'll get a fatal error (unless you manage to correctly spell the name of a different installed module).
Finally, the BEGIN block issue. Whether you use vars or our (or even my), you are declaring your variables at compile time but initializing them at run time. This leaves a window where you can end up using the variables before they are initialized.
I've been bitten by this and have seen several people get bitten by this in a variety of situations (some even here at the Monastery). Some of these incidents lead to the change to perlmod.pod that suggests using a BEGIN block to initialize your package variables. Although most of the incidents I've been able to dig up recently have involved someone doing something that you could argue they shouldn't be doing, I find that the BEGIN block allows, at least, "robustness in the face of stupidity", so I use it. Without the BEGIN block, you get a hard-to-diagnose failure that will probably suck up a lot of your time trying to figure out how to fix it.
Anyway, these cases have been plenty to convince me of the value of initializing global and file-scope variables inside of BEGIN blocks and have been enough to get someone else to change perlmod.pod and get those changes accepted. The BEGIN block only adds a slight bit of extra complexity.
So my standard package preamble is something like:
- tye (but my friends call me "Tye")package Xyz; use strict; use warnings; # highly optional but be sure to test with warnings on use base qw( Exporter ); use vars qw( $VERSION @EXPORT_OK ); BEGIN { @EXPORT_OK= qw [ FunctionAlpha FunctionBravo FunctionCharlie $calarDelta FunctionEcho $calarFoxtrot ]; }
In reply to (tye)Re: Standard Package Preamble
by tye
in thread Standard Package Preamble
by tadman
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