Beefy Boxes and Bandwidth Generously Provided by pair Networks
laziness, impatience, and hubris

Comment on

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

This is a generalized idiom, in the form of:

eval "something_that_might_fail(); 1;" or die "Message.";

In the general case, it makes sense because "something_that_might_fail()" could be some expression where "false" or "undef" are not out of band for success (ie, are perfectly valid return values even for a successful call).

In the specific case of "eval "require Some::Module; 1;" or die "Message.", your "Case 3" and "Case 3b" observations are accurate; require will return 1 on success. In this specific case, the 1; is redundant, though semantically it does maintain eval's return value to not be tied to the return value of the primary "thing that might fail."

On the one hand, one might say that "eval "require Foo; 1;" or die "Message";" is cargo culted. On the other hand, the idiom as a general tool is useful, and probably doesn't need to be optimized further just because this specific application doesn't need the 1;. It's healthy to decouple the thing that might fail's return value from the success sentinel, which is what the idiom does.

By the way; this is a very well researched question. Kudos.


In reply to Re: The 'eval "require $module; 1"' idiom by davido
in thread The 'eval "require $module; 1"' idiom by sedusedan

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 grasshoppers chirp...

    How do I use this? | Other CB clients
    Other Users?
    Others chilling in the Monastery: (5)
    As of 2018-02-24 13:01 GMT
    Find Nodes?
      Voting Booth?
      When it is dark outside I am happiest to see ...

      Results (310 votes). Check out past polls.