Q: Why can module B access A or C content?

Each package doesn't have its own instance of perl. When a module requires C, the C namespace is populated. Requiring a module is not that different from saying "our $C::foo" Any code that asks to see the C namespace can see every variable within it.

Q: Can A access B content without requiring B directly?

Yes, but don't do that. It will be a pain for future programmers to figure out what's going on.

Q: If a module is required twice, is there any mechanism like in C++ that can check if a module is required twice and in that case skip any redundant require's ?

See "perldoc -f require" Require records the modules it finds in %INC and will ignore redundant requests.

Q: Is the last require of A to D redundant? i.e. Can A access D without it?

No, it tells the next programmer that A intends to use D and keeps them from murdering you when they can't figure out where these D::foo methods are coming from. And if C ever changes its internal format to stop using D the code will still work.

In reply to Re: Scope of required modules by JStrom
in thread Scope of required modules by rapide

Title:
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, details, 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, summary, 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.