Something like this?

whacl> <tab><tab>
dig          help         llocks       need_commit  rcs          unlock
exit         list         lock         perform      touch_lm     untouch_lm

whacl> help rcs
Usage: rcs <rtr>

whacl> rcs rtrA
rcs(rtrA)> <tab><tab>
exit        help        lock        publish     syncronize  unlock

rcs(rtrA)> exit 
whacl> help lock
Usage: lock <rtr> <acl>

whacl> lock rtrA external-blocks
acl(rtrA,external-blocks)> <tab><tab>
block            help             list             unlock_and_exit

acl(rtrA,external-blocks)> block 192.168.254.1/32
block(192.168.254.1/32)> <tab><tab>
case     end      freshen  insert   mac      note     priv     status
delete   exit     help     list     modify   options  show     update

block(192.168.254.1/32)> delete
block(192.168.254.1/32)> exit 
acl(rtrA,external-blocks)> unlock_and_exit 
whacl> exit 

This goes something like:

use Q::Shell;
use Q::RCSShell;
use Q::ACLShell;
use Q::WhaclShell;

Q::WhaclShell->new ( prompt => 'whacl> ' )->loop();
exit 0;


#####

use Q::Shell;
package Q::WhaclShell;
our (@ISA) = qw( Q::Shell );

sub new {
  my ($class,%param) = @_;
  # blah blah SUPER::new
  $self->add_dispatch(
    rcs => [ \&_rcs, "short help", "long help" ],
    lock => [ \&_lock, "short help", "long help" ],
    # ...
  );
  return $self;
}

sub _rcs {
  my ($self,@arg) = @_;
  Q::RCSShell->new( )->loop(@arg);
}

sub _lock {
  my ($self,@arg) = @_;
  Q::ACLShell->new( )->loop(@arg);
}
1;

# and so on for Q::RCSShell and Q::ACLShell

package Q::Shell;

my %default_commands = (
  help => [ \&_help, "short help", "long help" ],
  exit => [ \&_exit, "short help", "long help" ],
);

sub add_dispatch { }
sub del_dispatch { }
sub _cmd_list { keys %{$_[0]->{_dispatch}} }
sub _help {
  # help - show all short help
  # help <cmd> - show long help for <cmd>
}
sub _exit { $_[0]->{done} = 1 }

sub new {
  # setup ReadLine
  # copy default_commands to $self->{_dispatch}
  return $self;
}

sub dispatch { # find and do <cmd> or warn whatever }

sub loop {
  # setup ReadLine with completions from $self->_cmd_list
  while ( not $self->{done} ) {
    # read and dispatch <cmd> <args>
    # reset ReadLine stuff (a command may have changed them)
  }
}

1;
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