Use the Net::FTP module

use Net::FTP;

$ftp = Net::FTP->new("some.host.name", Debug => 0)
  or die "Cannot connect to some.host.name: $@";

$ftp->login("anonymous",'-anonymous@')
  or die "Cannot login ", $ftp->message;

$ftp->cwd("/pub")
  or die "Cannot change working directory ", $ftp->message;

$ftp->get("that.file")
  or die "get failed ", $ftp->message;

$ftp->quit;