the thing

use strict;
use warnings;

opendir(HERE,'.') or die "Epic failure.\n";
my @paths = readdir(HERE);
closedir(HERE) or warn "Whatever.\n";

open(DATA,"data.txt") or die "Rename your text file 'data.txt'.\n";
my @data;
while(<DATA>) {
  chomp;
  next unless length;
  push(@data,$_);
}
close(DATA) or warn "Whatever two.\n";

foreach my $path (@PATHS) {
  next unless $path =~ /.*\.mp3$/io;
  my $newpath = shift @data, '.mp3';
  rename($path,$newpath);
}