For me it is strange that 'scalar do {};' and 'scalar do { if( 0 ){} };' have different outputs, as the codes look equivalent. Can someone explain a difference in the output?

if (EXPR) BLOCK returns either the value of BLOCK, or that of EXPR if it is false. I am certain it's mentioned somewhere in passing in the Perl docs, but I'm having trouble finding it at the moment; I'll update when I do.

Update: The text I was thinking of is in perlsub:

If no return is found and if the last statement is an expression, its value is returned. If the last statement is a loop control structure like a foreach or a while, the returned value is unspecified. The empty sub returns the empty list.

This "implicit return" stuff applies to do as well as to subs. As explained further down in this thread, in if (EXPR) BLOCK, when EXPR is false, the value of the last expression is that of EXPR, which is therefore returned.

In reply to Re: printing unitialized value of the 'do BLOCK' (updated) by haukex
in thread printing unitialized value of the 'do BLOCK' by rsFalse

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.