Aha!

I thought about your comments above. And I have a prototype for how it works.

package HostCycle;

$ftp_host = undef;

sub until { ; }
sub then  { ; }
sub cycle {my $self=shift;
  for $ftp_host (@ftp_host) {
     my $retval = $self->until($ftp_host);
     if ($retval) { $self->then($ftp_host); }
     else { ++$error_count; }

package SendOrder;
@ISA=qw(HostCycle);

sub until { # Wait for upfile to disappear }
sub then  { # Upload orderfile and upfile  }

package GetOrder
@ISA=qw(HostCycle};

sub until { # Wait for downfile to disappear }
sub then  { # Download all files in directory  }
[download]

And of course regarding runtime alteration of code blocks: when was the last time you needed that? Answer: when you are trying to create your model as metaphorical to the language as opposed to creating a model with the language. Douglas Hofstadter in "Goedel, Escher, Bach: The Eternal Golden Braid" tried to say that we needed self-modifying, self-reflective languages. But in actually we just need to ability to modify and study structures.