Net::FTP can do this, is has a "quot" method to send commands that it doesn't have specific support for:

use Net::FTP;
my $ftp = Net::FTP->new('ftp.rge.com');
$ftp->login('ftp','anon@');
my $okay=$ftp->quot('HELP');
my $code=$ftp->code;
my $message=$ftp->message;
print "[$okay] [$code] [$message]\n";
[download]

Prints:

$ perl tester
[2] [214] [The following commands are recognized (* =>'s unimplemented
+).
   USER    PORT    STOR    MSAM*   RNTO*   NLST    MKD*    CDUP 
   PASS    PASV    APPE*   MRSQ*   ABOR    SITE    XMKD*   XCUP 
   ACCT*   TYPE    MLFL*   MRCP*   DELE*   SYST    RMD*    STOU*
   SMNT*   STRU    MAIL*   ALLO*   CWD     STAT    XRMD*   SIZE 
   REIN*   MODE    MSND*   REST    XCWD    HELP    PWD     MDTM 
   QUIT    RETR    MSOM*   RNFR*   LIST    NOOP    XPWD 
Direct comments to ftp@rge.com.
]
[download]

Some of the methods come from Net::Cmd, which Net::FTP is derived from. See the docs for both.