The error in your code has been already pointed out by merlyn and somebody else (how fast are these people ;-), but I'd like to add a more "idiomatic" version of your code. You should return mp3 files only (if you are after them ;-) ...

#!/usr/bin/perl
use strict;
use warnings;
use Carp;
 
 my $dir = '/home/musc';
 my @mp3 = getSongs( $dir );

 for my $song (@mp3) {
    print "$song\n";
 }

 sub getSongs
{
 my $dir = shift;
 my @files;
 if( -d $dir ) {
    opendir(my $dirhandle, $dir) or croak "$dir $!";
    @files = grep /\.mp3$/, readdir $dirhandle;
    closedir $dirhandle
 }
 else {
    carp "don't know about $dir\n"
 }
 return @files;
}
[download]

Regards

mwa