push @attach_list, 'Bach.jpg';
push @attach_list, 'workshop notes.pdf', 'Booking form.pdf';
push @attach_list, qw(testaaa.xls testx.xlsx wordtest.docx); # qw() only if the file names don't have spaces in them
##</code><code>##

for $to_em (@to_email_list) {
   ...
   $smtp->to($to_em);
   ...
}