I am trying to understand two snippets of code, that have different behaviors that I do not immediately grasp. Consider: 
use strict;
use Data::Dumper;

my @res = grep $_ split(",", "a,b,c,d,,f,,h");
print Dumper(\@res);

my @res2 = grep { $_ } split(",", "a,b,c,d,,f,,h");
print Dumper(\@res2);

[download]
When ran, it returns 
$VAR1 = [
          'a',
          'c'
        ];
$VAR1 = [
          'a',
          'b',
          'c',
          'd',
          'f',
          'h'
        ];

[download]
I understand the second example, as I am evaluating the "truth" of the elements I am iterating over. I do not understand the output of the first dump, when given just "$_". I did look at grep's perldoc, hoping for an ounce of clairvoyance, but to no avail.

In reply to Confusing grep behavior by dextius

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.