You are using Perl, but your question pertains to the shell that evaluates the command in backticks. To solve this, you have to see, why your shell doesn't like the command.

Besides take a look at perlop. There is a section about quoting (and you should quote, what you are giving to the shell) stating about the command given in backticks: "How that string gets evaluated is entirely subject to the command interpreter on your system."

For example, when I try to run your code on my Ubuntu I am getting something like 

#!/usr/bin/perl

use strict;
use warnings;

my $cmd = "------------- Hello World ------------";
my $result = `echo $cmd | grep '\-\-\-\-'`;
print $result . "\n";

[download]
grep: unknown option »----«

[download]

I am assuming however, that you don't really want to search a string in Perl that way (there are better ways), but to learn something about calling external commands.

In reply to Re^3: sh: -c: line 1: syntax error near unexpected token `|' by lune
in thread sh: -c: line 1: syntax error near unexpected token `|' by perl@1983

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.