You can do essentially the same thing from Perl like this (untested):

open(FTP,'| ftp -n ')
  or die "Couldn't run FTP: $!\n";
my $ofh = select(FTP); $|=1; select($ofh);
print FTP "open $IP\n";
print FTP "quote USER $user\n";
print FTP "quote PASS $pass\n";
print FTP "lcd\n";
# and so forth
[download]

But you probably are better off installing Net::FTP, if nothing else for better error handling and portability. It's a pure-Perl module, so should be easy to install even without any special system privileges.