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Re^2: How to import "global" variables into sub-scripts from main script?

by Polyglot (Friar)
on Mar 23, 2021 at 13:48 UTC ( #11130192=note: print w/replies, xml ) Need Help??


in reply to Re: How to import "global" variables into sub-scripts from main script?
in thread How to import "global" variables into sub-scripts from main script?

Bliako, thank you. While some here seem bent on forcing me into their mold, or just writing me off and voting me down, you have gone the extra mile to give me a truly useful set of suggestions. While I appreciate the time you spent on all of it, I will likely only be able to implement your first suggestion--that of putting variables into a package and calling that. THAT is something I never knew was possible before, and that sounds like a perfect solution in my use case. I wonder why no one else does it this way or bothered to suggest this possibility. Thank you so much!

Really, I wish I could do OO programming. I've tried. I've read the chapters on it in "Programming Perl" (Third edition) multiple times, and have made attempts at using it, only to meet with total failure. My syntax errors simply follow my general lack of understanding. It's always been above me. Perhaps if I had an excellent teacher who could once explain it for me in a way that made sense to me, it might be different--but, just like math, the typical case is that the teacher has almost a language and logic of his/her own--one that is too esoteric for many minds. I have managed to use the my $something = $cgi->param('something'); method from the CGI module, but many other modules are too hard for me to grasp. When one needs to start escaping or doubling the "funny characters" in front of the variables, or start using those "->" references, that's usually where I get lost--I no longer have any idea when to use which form.

But I think I will put that Variables.pm file to practice shortly! (I'd always put all of that at the top of my main script, but it makes a large chunk of material to have to scroll past every time I want to navigate between the required/used files and the code.)

Blessings,

~Polyglot~

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Re^3: How to import "global" variables into sub-scripts from main script?
by bliako (Monsignor) on Mar 23, 2021 at 17:03 UTC
    But I think I will put that Variables.pm file to practice shortly

    right but beware that there may be dragons if you modify those variables in subscripts. There may be cases (which I am not aware of, I am not a Perl expert) where changing a package variable will not be reflected to other users of said package (e.g. one of your various subscripts). For read-write variables it's not a good way and I will not use myself.

    some here seem bent on forcing me into their mold

    Oh come on! (respectfully said). From my experience this is hardly the case with PM (compare to Stack overflow by posting this exact question there -- even your super-ground -- good story btw -- will not protect you from the flaming lightnings they will throw at you). Perl is a fertile ground for TIMTOWTDI and Perl culture preaches it. Perl allows you to do a lot of things, even shooting your foot, some people, understandably frown on extremely un-productive or buggy solutions which can lead to future problems (e.g. maintainability). If I may say so (and I don't wish to start a conversation about this side-issue): saying that your case is special because you are the only maintainer, is not an argument to the good points presented here (about general programming practices at least). You are offered good solutions which require that you change some of your programming habits, "change gear", "grow up" as a user of a programming language. Case-in-point is OO (actually the free style of Perl OO). It can reduce code-lines (which you are interested) tremendously by re-using code, it can encapsulate data and transformations which will make your code more maintainable, easier to handle. It does not require super-human abilities but it requires to program along certain "molds". And btw the -> is used just as you will be using it in a hashref (which essentially is what an OO object is, a mere hashtable with data AND subs as values). Try posting a question about OO and see what happens.

    bw, bliako

      > There may be cases (which I am not aware of, I am not a Perl expert) where changing a package variable will not be reflected to other users of said package

      Do you mean mod_perl and similar parallel preloading environments?

      map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

        I don't know a lot about mod_perl so I did not have that in mind. Parallelism can be an issue when modifying package vars in different threads (as with anything else). But as there are different ways to import a module (e.g. use, require but especially do (and eval) which asker uses a lot) and there are also ways to reload a module at runtime (e.g. Module::Refresh) I thought it's better to leave a questionmark there rather than being absolute. Given also that there are other safer ways to achieve read-write effect. Personally I can't stand things like: $DBI::errstr, whereas $XYZ::DEBUG = 1 is tolerable.

        What's your opinion? Can we rely on the state of a package's variables modified after loaded (not in mod_perl, threads)?

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