Maybe it's not the FTP sites, but a firewall issue.

You might want to do :

export FTP_PASSIVE=1
[download]

before starting up perl. From the Net::FTP documentation: Passive - If set to a non-zero value then all data transfers will be done using passive mode. This is not usually required except for some dumb servers, and some firewall configurations. This can also be set by the environment variable FTP_PASSIVE.

Hope this helps.

Liz