Thank you for the suggestions. Alas, it seems I am still missing an important piece of knowledge. I changed my code to this:

find(\&offenders, $dir);

sub offenders{

    # recurse directories
    $File::Find::prune = 0;

    # there are some shared directories
    # that we do not want to include

    my @dirs = 
        '\/home\/engineering\/dev\/share';
   
    foreach my $z (@dirs){
        #print "$z eq $File::Find::dir\n";
        return if ($File::Find::dir =~ m/$z/)
    }

    # do not include links
    return if (-l);

    # owner of file but skip
    # if owner is not a user
    # (uid < 500)
    #
    #return if ($uid < 500);
    $uid = (lstat($_))[4];
    if (-d && $uid < 500){ 
        # check do not recurse these
        # dirctories
        $File::Find::prune = 1;
        print "UID is $uid, skipping $File::Find::dir, $File::Find::na
+me, $_\n";
        return; 
    }

    # scan only regular files
    if (-f){
        $uname = getpwuid $uid;

        # gather name of file
        $fname = $File::Find::name;

        # size of file (kb)
        $size = (lstat($_))[7];
        $size = int($size/1000);

        # keep running total of each
        # user's space use
        $size{$uname} += $size;
    }
}
[download]

This skips everything. Here is the output:

UID is 0, skipping /home, /home, .
[download]

Then the program exits.