#!/usr/bin/perl

use strict;
use warnings;

#####################################################################
#                              
              #
#    script which scans recursively all folders based on         #
#    the current directory and renames audio file-names        #
#    to a burn-friendly format              
      #
#               
               
      #
#####################################################################


#             constants &nb
sp;              #

use constant MAX_FILENAME_LENGTH => 31;

#            main script              
  #

print "start renaming files....\n";

scanDir();

print "finished renaming files....\n";

#            functions &nb
sp;              #

sub scanDir {

    # open current directory
    
    opendir(CURDIR, ".") or die "could not open directory! \n";
    
    # iterate over directory entries
    
    while(my $dirEntry = <CURDIR>) {

        # skip "." and ".."
    
        if($dirEntry eq "." || $dirEntry eq "..") {
            next;
        }

        # if we encounter a audio-file
    
        if(-f $dirEntry && $dirEntry =~ m/(.*mp3$)|(.*ogg$)/) {
            renFile($dirEntry);
        }
    
        # if we encounter a directory, descend into it and start recursion    
    
        elsif(-d $dirEntry) {
            chdir($dirEntry) or die "could not open directory $dirEntry! \n";
            scanDir();
        }
    
    }
    return 0;
}



sub renFile {


    my $newFileName = my $oldFileName = shift;

    # delete all special chars

    $newFileName =~ s/[^a-zA-Z0-9_\,-]//;

    # shorten file name if necessary and rebuild filename

    $newFileName = substr($newFileName, 0, MAX_FILENAME_LENGTH) . substr($oldFileName, -4)
    if(length($newFileName) > MAX_FILENAME_LENGTH);

    rename ($oldFileName, $newFileName) or die "could not rename file $oldFileName !\n";

    return 0;
}

 ./rectFileNames.pl
start renaming files....
readline() on unopened filehandle CURDIR at ./rectFileNames.pl line 37.
        (Are you trying to call readline() on dirhandle CURDIR?)
finished renaming files....