I am not an expert on SEC filings or the Edgar database, but after a few minutes of poking around the README
file and docs
directory it looks like everything would still be simpler with ftp unless you are a screen-scraping wizard.
As I have just learned, each company that files with the SEC has a CIK number. In your example, the CIK number for IBM is 51143. All of IBM's filings live in that directory ftp://ftp.sec.gov/edgar/data/51143. From the explanation in the README it seems that prior to Edgar 7.0 (starting in the year 2000) all of each company's filings were stored in one directory, but because of problems with overwriting documents when ammendments were submitted, everything is now stored in sub directories based on the accession number of the documents. This might be why it appears that information is per-day. Fortunately, it looks like the SEC provides an index of filings for each quarter by company name or type of filing so you don't have to mess around with slogging through every sub-directory to find the information you need. The only benefit I see from the http interface in your example is that your search focused on filings related to change of ownership. However, I gather that these are related to a known subset of forms (4, K-8) and this information is available in the index, so you could subset the information yourself.
So, if it were me I would probably move forward in two stages using Net::ftp to 1) grab indices and subsetting the records I need based on company and filing-type to create a list of the files I want to get, and then 2) and grab those files with Net::ftp again.