Here is an answer I received via email. Thoughts?

"The thing about Perl is that (excluding explicit returns), Perl will return the last value seen in the function. With your "unless" example, the unless is explicitly not going to ever evaluate because the condition is predetermined to be false.

So the entire unless statement is not evaluated and the return is the last evaluation (your variable assignment).

'If' works differently because it does no pre-evaluation. It evaluates the if block every time to determine if the conditional is met. So the last "evaluation" in the function is the if block (which returns nothing, just like your function).

The magic happening is the pre-evaluation conditions of the unless block. Unless ONLY fires if the condition is met. If fires every time, but performs an automatic JMP outside of that block (with a null return) as soon as the condition evals to false."

In reply to Re^2: unless versus if ( ! ) inside a subroutine by Wheeler
in thread unless versus if ( ! ) inside a subroutine by Wheeler

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.