The worst thing about long if-elsif-else chains is their performance, but you are talking about an interactive aplication, so you don't need to worry about performance and chained if-elsif-else's will not be so bad.

Anyway, let my suggest an alternative OO aproach: define a class for every command you support, i.e.: MyApp::Command::ls, MyApp::Command::cp, etc.

Then, in every command class define the set of methods you need, i.e. parse_args(), run(), print_output(), etc.

And then use the perl OO notation to dispatch commands: 

while(read_cmd()} {
  eval {
    $cmd_name=~/^\w+/ or die "invalid command";
    my $cmd_class = "MyApp::Command::$command_name";
    my $cmd = eval { require $cmd_class; $cmd_class->new };
    if ($@) die "unknow command $cmd_name ($@)\n";
    $cmd->parse_args(@args) or die "...";
    $cmd->run(@args) or die "...";
    etc();
  };
  print $@ if $@;
}

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This way, adding new commands is very easy, just create new classes for them and drop them on the rigth directory. It also allows for simple code reuse via inheritance.

In reply to Re: how to deal with 20 commands by salva
in thread how to deal with 20 commands by bahadur

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