Bareword filehandles have their places, particularly in simple scripts, where there really is almost no difference between them and lexical file handles — declaring a lexical at file-scope has almost exactly the same effect, and exactly the same effect if the convention of maintaining a 1:1 mapping between files and packages is followed.

However, a sub that opens a file and returns a handle should always return a lexical filehandle, unless its purpose is to return "THE" singleton filehandle for some resource, and in that case it should be using our to store the filehandle in a global. Generally, bareword filehandles should be limited to the mainline code in the top-level script. Subroutines should use lexical filehandles and modules should only contain subroutines.

In Perl, all "globals" are actually package variables, although a few special names (including the "punctuation variables") are forced into package main. The distinction is that a "global" variable is stored in a symbol table slot in some package. Package variables in Perl are globally-accessible, since the package namespace is itself global. The our keyword creates lexically-scoped aliases to package variables and is very convenient when needed.

A lexical declared at file scope is effectively a global variable and has all of the same problems in complex code, with the additional risk that file-scope lexicals can be shared across packages if multiple packages are defined in the same file. Global variables are generally dangerous in programming and I strongly favor the use of bareword filehandles at top-level in preference to declaring lexicals at file-scope and thinking that you are safe.

Perhaps the best would be to default to use bareword::filehandles in package main and no bareword::filehandles in other packages. This keeps the feature where it is most useful, to avoid the "head in sand" problem of using file-scope lexicals in the main script, while still pushing modules to avoid the feature unless it really is appropriate.

In reply to Re: Is there a problem with using barewords as filehandles ? by jcb
in thread Is there a problem with using barewords as filehandles ? by syphilis

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.