yes, you're right. both $cmd and @args will be received through the socket. hmm... what about this one:

#!/usr/bin/perl -w

{
    package Net::SMTP::Server::Client2::Subclass;
    use strict;
    use vars qw/@ISA/;
    use Net::SMTP::Server::Client2;
    @ISA = qw/Net::SMTP::Server::Client2/;

    my %_pcmds = ( HELO => \do { print STDERR "hello\n" }
                 );

    our $eval_command = sub {
              my ($self, $cmd, @args) = @_;
              my $hash = (__PACKAGE__ =~ /Subclass$/) ? '$_pcmds' : '$
+_cmds';
              $cmd = "&{$hash"."{$cmd}}(\$self, \\\@args)";
              eval $cmd or return(defined($self->{MSG}));
              };
    &Net::SMTP::Server::Client2::eval_command = \$eval_command;

    sub new {
        my ($class, $sock) = @_;
        my $self = $class->SUPER::new($sock);
        bless $self, __PACKAGE__;
    }


    sub get_message {
        my $self = shift;
        my ($cmd, @args);
        # [...}
        # do everything the super class does, up to this point:

        if (exists $_pcmds{$cmd}) {
            $eval_command->($self, $cmd, @args);
        }
        else {
            $self->SUPER::eval_command($cmd, @args);
        }
    }

   1;

}
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i've never done that before, but at least the compiler doesn't complain.