That may not work correctly, depending on what characters are in the file name: 

$ ls -l
total 0
-rw-r--r-- 1 john john 0 Feb  1 20:23 four
-rw-r--r-- 1 john john 0 Feb  1 20:23 one
-rw-r--r-- 1 john john 0 Feb  1 20:23 two ? three
$ ls | perl -nle 'BEGIN { $counter = 0 }; $old = $_; $new = "caption" 
+. "$counter" . ".txt"; rename( $old, $new ); $counter++;'
$ ls -l
total 0
-rw-r--r-- 1 john john 0 Feb  1 20:23 caption0.txt
-rw-r--r-- 1 john john 0 Feb  1 20:23 caption1.txt
-rw-r--r-- 1 john john 0 Feb  1 20:23 two ? three

[download]

Better to use perl's built-in glob function: 

$ ls -l
total 0
-rw-r--r-- 1 john john 0 Feb  1 20:28 four
-rw-r--r-- 1 john john 0 Feb  1 20:28 one
-rw-r--r-- 1 john john 0 Feb  1 20:28 two ? three
$ perl -e '$counter = 0; for ( <*> ) { $old = $_; $new = "caption" . "
+$counter" . ".txt"; rename( $old, $new ); $counter++; }'
$ ls -l
total 0
-rw-r--r-- 1 john john 0 Feb  1 20:28 caption0.txt
-rw-r--r-- 1 john john 0 Feb  1 20:28 caption1.txt
-rw-r--r-- 1 john john 0 Feb  1 20:28 caption2.txt

[download]

In reply to Re: Renaming all files in a directory by jwkrahn
in thread Renaming all files in a directory by Aldebaran

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.