The Apache::Request module gives you an easy way to get form content, including uploaded files. In order to add file upload functionality to your form, you need to add two things.

First, you'll need to add a form field which is type file. This will put a browse button on the form that will allow the user to choose a file to upload.

Second, you'll neet to make sure to add, to the form tag the following:
enctype="multipart/form-data"

You won't be able to upload a file unless you have added this to the form tag.

In your code, you'll need to take a few extra steps to actually retrieve that file that has been uploaded. Using the following form() method will allow you to have a standard function that handles all of your forms, and does the right thing in the event that there was a file uploaded. You can put this function in your mod_perl handler, or in whatever module you want.
sub form {
use Apache::Request;
my $r = Apache->request();
my $apr = Apache::Request->new($r);
my @keys = $apr->param;

my %form;
foreach my $key(@keys) {

my @value = $apr->param($key);
next unless scalar @value;

if ( @value > 1 ) {
$form{$key} = \@value;
} else {
$form{$key} = $value[0];
}
}

my $upload = $apr->upload;
if ($upload) {
$form{UPLOAD} = $upload;
}

return \%form;
}

In your code, you can get the contents of the form by calling this function:
my $form = Your::Class::form(); # Wherever you put this function

The value returned from this function is compatible with CGI.pm and other modules such as CGI::Lite Which is to say, the function returns a hashref. The keys of the hash are the names in your form. The values in the hash are the values entered in those fields, with the exception that a multiple select list with multiple things selected will return a listref of the selected values.

If your form contained a file upload element, then $form{UPLOAD} will contain a file upload object, which you can make calls back into.

For example:
my $form = Your::Class::form(); # Wherever you put this function
if (my $file = $form->{UPLOAD}) {
my $filename = $file->filename; # If you need the name

# And, if you want to save the file at $filelocation ...
open F, ">$filelocation";
my $filehandle = $file->fh;
while (my $d = <$filehandle> {
print F $d;
}
close F;
}

That should give you the general idea of how this works. This lets you have a generic form handler that does "normal" forms as well as file upload forms, in mod_perl, without having to mess with CGI.pm, and without having to do custom things when you have a file upload.

You will need to see the documentation for Apache::Upload for more information about how to deal with the file upload object once you have it. Note that the Apache::Upload docs are embeded in the Apache::Request documentation, so you'll need to look there for that information.