use strict;
use warnings;
use File::Copy qw(move);

my $input_dir = ...;
my $output_dir = ...;

opendir(my $dh, $input_dir) or die "Can't open dir $input_dir: $!";
my @mp3 = grep { /\.mp3/ } readdir($dh);
closedir $dh or die "Can't close dir $input_dir: $!";

foreach my $fn_old (@mp3) {
  my $fn_new  = $fn_old;

  # filtere den neuen Filenamen
  $fn_new =~ tr/a-zA-Z.0-9/_/cs;
  $fn_new =~ s/_\././g;

  # verschiebe die Datei
  move("$input_dir/$fn_old","$output_dir/$fn_new") 
    or die "move of '$fn_old' failed: $!";
}