One obvious issue would be if you don't have write permission on the file. Check with

use Carp;

my $file = '1.mp3';
croak("Cannot write to file $file")
    if(!-w $file);
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You might like to check some of the resources here, for example Fixing mp3 tags for Android 2.0 contains a tested script that uses MP3::Tag to set values in pretty much the way you want.