You grep expression is in the form:grep EXPR,LIST. But EXPR is fixed as $var1 - not a regexp or code block.

grep will return the whole list or an empty list depending on whether $var evaluates to true or false. Consider: 

my @arr1 = ('a');

foreach my $var1 (0, 1) {

  if( grep($var1, @arr1) ) {
        print "match $var1\n";
    }
  else {
    print "fail $var1\n";
  }

}

[download]
  • nothing is returned when $var1 is 0 (false)
  • the entire list is returned when $var1 is 1 (true)

    • Update: Here's a sample usage: 

    #!/usr/bin/perl
use warnings;use strict;

my $paid = 0;  # :-(

my @shopping =
  (
   'twinkies','coffee',
   (grep !$paid => 'gruel', 'cabbage', 'cordial'),
   (grep $paid => 'caviar', 'truffles', 'champagne'),
  );

print "@shopping";

    [download]

    In reply to Re^2: Weird grep behaviour by snoopy
    in thread Weird grep behaviour by chrism01

    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.