Try the option TimeOut in the constructor. By default this option will take as 120 check the link "http://perldoc.perl.org/Net/FTP.html"

use Net::FTP;
$ftp = Net::FTP->new("some.host.name", Debug => 0, Timeout => 300);
$ftp->login("anonymous",'-anonymous@');
$ftp->cwd("/pub");
$ftp->get("that.file");
$ftp->quit;
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