NET::FTP is spelled 'Net::FTP'. Case matters on some systems.

Update: To clarify tye's reply, and my own post, on case-insensitive systems, this will work (assuming we're trying to use the Net::FTP module):

use NET::FTP;
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but this won't:

my $ftp = NET::FTP->new("hostname");
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On case-sensitive systems, the first statement will fail, as would the second if it ever got executed.