A good rule of them i like to apply, is use "if (cond){ block }" only if block is more then one statement.

As for using "A or B" vs "B unless A" .. I like to make the "main" action be the first one, so that people skimming your code get an idea of what you are doing without reading hte whole line. But in the examples you provide, deciding what the "main" action is depends largely on your perception of the greater context...

Given such a short bit of code, it probably doesn't matter much. However, if you were doing a big chunk of input/data validation, with lots of different warnings in differnt cases, I'd use... 

warn "blah blah" unless A;
warn "yak yak" unless B;
warn "bafkjlkajaksjdf;lkjas;kaj;aksdf;kjalkjas;dkf"
   unless C;
warn "blblblblblbblblblblbl"
   unless (D or E);

[download]

if you're doing a lot of processing, and the warning is just an afterthough in one section of hte processing, then i'd use or... 

doSomething();
something->else();
third_thing() 
   or warn "something didn't work quite right";
still(processing);

[download]

In reply to Re: Style: expr or warn vs. if..warn? by hossman
in thread Style: expr or warn vs. if..warn? by FoxtrotUniform

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.