Beefy Boxes and Bandwidth Generously Provided by pair Networks
The stupid question is the question not asked

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??

Nearly every Perl script I write follows this format:

#!/usr/bin/perl -w use strict; use Other::Modules qw< ImportedFunction >; use vars qw< $Globals >; Main( @ARGV ); exit; sub Routine { ... } BEGIN { my $static= "Initial value"; sub usesStatic { ... } } sub Main { my $putMainVarsHere; ... } __END__
So you can prevent your subroutine from accessing your "main" variables by putting them where I wrote $putMainVarsHere.

This style has evolved for quite a while and there are specific reasons for almost every aspect of it. I find it catches quite a few errors for me.

I was going to explain my reasons for most aspects of this style, but I decided that that would be more appropriate elsewhere.

(updated twice)

Update: Here are some justifications for some of my decisions that I collected quite a while ago planning to write this up more formally. Instead I've just moved them from my scratchpad to here:

  • #!/usr/bin/perl is the standard place for Perl as declared by Larry himself. Even if you install /usr/local/bin/perl, please also put a link in /usr/bin and please use #!/usr/bin/perl in scripts that you make public
  • Explicitly listing what you want exported from a module means that when I read your code and see GnarfleTheGarthock(), I can search for "GnarfleTheGarthock" and I'll find the "use Coneheads qw( GnarfleTheGarthock );" line and know where to go find documentation and/or code for that subroutine even if Gnarfle or Garthock appear to be an "obvious" Coneheads reference to _you_ ;)
  • Lets you distinguish file-scoped lexicals declared at the top of your scripts that act as global variables from "sub Main" lexicals that should not be directly accessed by other subroutines.
  • Gives you a handy place for a break point ("c Main") when debugging (stepping over module and global variable initialization can get boring)
  • Since Perl's "global destruction" phase doesn't obey reference counts, it can cause problems when objects refer to each other. "sub Main" can aid debugging of such destruction issues because you can break after returning from Main()...
  • Main(@ARGV) allows you to parse the command line via @_ which makes it easier to refactor that code later
  • exit; means that no code outside of a sub below will get executed. This can bite you, but I really like it because I know I don't have to search the entire script looking for random bits of code.
  • That previous item also forces you to use BEGIN to initialize any "static" lexicals, which ensures that you never call a subroutine before any "static" lexicals that it uses are initialized
  • The BEGIN block also prevents "will not stay shared" warnings that break the use of file-scoped lexicals in subroutines with Apache::Registry under mod_perl

        - tye (but my friends call me "Tye")

In reply to (tye)Re: Stupid question by tye
in thread Stupid question by code24

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?

    What's my password?
    Create A New User
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others musing on the Monastery: (3)
    As of 2020-10-26 03:52 GMT
    Find Nodes?
      Voting Booth?
      My favourite web site is:

      Results (250 votes). Check out past polls.