Multiple 'use vars' lines

doran has asked for the wisdom of the Perl Monks concerning the following question:

Is it okay to use vars mulitple times? I sometimes find it would be easier to document my code if I can use vars multiple times, with comments in between:

#!/usr/bin/perl -Tw
use strict;

# These are for one thing
use vars qw/$foo $bar $baz/;

# These are for another thing
use vars qw/$bimm $bamm $boom/;

# Now do one thing or another...
[download]

Is this discouraged for some reason or, worse yet, might it break something?

Thanks,
Doran...

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Re: Multiple 'use vars' lines by japhy (Canon) on Mar 21, 2001 at 00:33 UTC
Absolutely nothing wrong with it. Try it. `japhy` -- Perl and Regex Hacker	[reply]
Re: Re: Multiple 'use vars' lines by doran (Deacon) on Mar 21, 2001 at 00:44 UTC
Thanks, I tried it (actually before posting), and it seems to work fine. I just wanted to make sure there was nothing bad happening that I didn't know about. I don't recall ever using a module multiple times in a single script and just wanted to make sure it didn't come back to bite me. -db	[reply]
Re: Multiple 'use vars' lines by dws (Chancellor) on Mar 21, 2001 at 01:26 UTC
An easy (and educational) way to get answers to questions like this is to consult the source. `vars.pm` is quite short, consisting essentially of a single 30-line `import` routine, of which ~10 lines are interesting. Even if parts of the code use uncommon (though hardly non-standard) trickery, it is quite easy to answer the specific question of whether repeated applications of `use vars` are cummulative. Source is your friend. It will answer all sorts of questions if only you take the time to ask it.	[reply] [d/l] [select]
Re: Multiple 'use vars' lines by larsen (Parson) on Mar 21, 2001 at 03:41 UTC
It's a good practice to use many `use vars` lines to group variables with common semantic meaning. Now two interesting points from the documentation: use vars predeclare global variable names (obsoleted by our()) and... An `our' declares the listed variables to be valid globals within the enclosing block, file, or `eval'. That is, it has the same scoping rules as a "my" declaration, but does not create a local variable. If more than one value is listed, the list must be placed in parentheses. The `our' declaration has no semantic effect unless "use strict vars" is in effect, in which case it lets you use the declared global variable without qual ifying it with a package name. (But only within the lexical scope of the `our' declaration. In this it differs from "use vars", which is package scoped.)	[reply] [d/l]
Re (tilly) 2: Multiple 'use vars' lines by tilly (Archbishop) on Mar 21, 2001 at 03:55 UTC
The existence of a new way to do it does not make the old obsolete. And as long as I honestly believe that it is worse than what it replaces, I won't use it.	[reply]