print ++($foo = "99");    # prints "100"

##</code><code>##

if ($sequence_number++ gt "99999") {

##</code><code>##

if (($sequence_number)++ ...) {
    $sequence_number = "00001";
}
else {
    ($sequence_number)++;
}

##</code><code>##

my $sequence_number = "00001";
use_seq_no($sequence_number);

while (...)
{
    if (++$sequence_number eq "99999")
    {
        $sequence_number = "00001";
    }

    use_seq_no($sequence_number);
}

sub use_seq_no
{
    ...
}