You are getting a directory listing because that is what you are asking for. (the end of your path is a directory, not a file)

my $url = 'ftp://ftp.symantec.com/public/english_us_canada/antivirus_d
+efinitions/norton_antivirus_corp/';
[download]

You will most likely not be able to get the HTML page you seek, as it seems to be a dynamically generated directory listing by either the ftp server or your browser (I dont know what kind of FTP server symantec uses, and what OS and browser version you used to get that HTML with so I couldnt really say, although I am leaning towards Windows and IE which means it was your browser is generating it). (Notice the TITLE)

<TITLE>Directory listing for /public/english_us_canada/antivirus_defin
+itions/norton_antivirus_corp/</TITLE>
[download]

Just changing ftp:// to http://, I suspect would not work, since the ftp.symantec.com is likely not going to respond to HTTP requests, and my (strong) suspicions are that the your browser is generating the HTML.

You should try Net::FTP and check modification dates on the files you are wondering about. Since I don't know the criteria you want to use to test how old or new these files are, I can't help you there, but you should be able to find plenty of date comparison and manipulation modules on CPAN which will surely suit your needs.

-stvn