sub trim;
...
    my ($error) = 0;
    my @other_addresses = split( /\n/, $email_list );
        foreach (@other_addresses) {
            trim $_;
            my $ok = Email::Valid->address($_);
            $error++ if(!$ok);
            print "address($_) = $ok<br>";
            print "error ".$error."<br>";
        }

    $error_message .= "$error Email list contains an invalid email address.<br
+>" if ($error > 0);

...
sub trim {
   $_[0] =~ s/^\s+//;
   $_[0] =~ s/\s+$//;
   $_[0];
}
}