#!/usr/bin/perl
use strict;
use warnings;
use File::Find;
my $dir = shift;
find(\&print_name_if_file, "$dir");

sub print_name_if_file {
      print "$_\n" if -f;
}

##</code><code>##

[racket@ibmlap perl]$ ./filechng.pl testdir
file4.pdf
file5.pdf
file2.pdf
file3.pdf
file10.pdf
file7.pdf
file9.pdf
file8.pdf
file1.pdf
file6.pdf

##</code><code>##

[racket@ibmlap perl]$ ls -al testdir
total 56
drwxrwxr-x  2 racket racket 4096 Mar 24 14:59 .
drwxrwxr-x  3 racket racket 4096 Mar 24 15:08 ..
-rw-rw-r--  1 racket racket    0 Mar 24 14:59 file10.pdf
-rw-rw-r--  1 racket racket    0 Mar 24 14:58 file1.pdf
-rw-rw-r--  1 racket racket    0 Mar 24 14:58 file2.pdf
-rw-rw-r--  1 racket racket    0 Mar 24 14:58 file3.pdf
-rw-rw-r--  1 racket racket    0 Mar 24 14:58 file4.pdf
-rw-rw-r--  1 racket racket    0 Mar 24 14:59 file5.pdf
-rw-rw-r--  1 racket racket    0 Mar 24 14:59 file6.pdf
-rw-rw-r--  1 racket racket    0 Mar 24 14:59 file7.pdf
-rw-rw-r--  1 racket racket    0 Mar 24 14:59 file8.pdf
-rw-rw-r--  1 racket racket    0 Mar 24 14:59 file9.pdf