Perl FAQ 5.9

Several reasons. One is because backticks do not interpolate within double quotes in Perl as they do in shells. Let's look at two common mistakes:

     $foo = "$bar is `wc $file`";  # WRONG

This should have been:

     $foo = "$bar is " . `wc $file`;

But you'll have an extra newline you might not expect. This does not work as expected:

$back = `pwd`; chdir($somewhere); chdir($back); # WRONG

Because backticks do not automatically eat trailing or embedded newlines. The chop() function will remove the last character from a string. This should have been:

      chop($back = `pwd`); chdir($somewhere); chdir($back);

You should also be aware that while in the shells, embedding single quotes will protect variables, in Perl, you'll need to escape the dollar signs.

    Shell: foo=`cmd 'safe $dollar'`
    Perl:  $foo=`cmd 'safe \$dollar'`;
    

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