Table of contents

Embedded Language Support

Since version 0.50.00, mcl supports Perl scripting. All scripts executed
by mcl reside in the ~/.mcl directory and end with .pl. This section assumes
that you have some knowledge of Perl.

Since version 0.52.00 mcl also supports embedded Python scripts. Those
scripts end with .py. Pretty much everything below applies to Python: just
replace .pl with .py.

To choose between Perl or Python, simply supply plugins=perl or plugins=python
in the configuration file. If you specify multiple interpreters, they are
stacked. That is, the first interpreter gets the first shot at all triggers
and then the second one gets called with whatever the result of the first
pass was. Pattern matching, substitution and variable extraction is only
called in the first interpreter however.

When mcl starts up, it will execute the init script - i.e.
~/.mcl/sys/ You don't want to modify that file - it may be changed
with new versions of mcl. Instead modify the "" file. Generally,
files in sys/* are some that will be modified with new versions of mcl.

The init script can contain anything - assignments to variables, definition
of functions you want available globally, etc.

Also, in the second part of the initialization, mcl will load *all* the
scripts that are loaded in ~/.mcl/auto/*.

The first time you connect to a MUD, mcl will load the script with its name
(e.g. ~/.mcl/ if you connect to 'ar'). This works as the init script.

Before exiting, Perl will run the sys/ script. This can be useful for
saving custom configuration options. Again, this is a system script and
you should use various hooks to have things run at exit time.

If ~/.mcl/sys/ is 

Running code

You can run perl code from mcl by several means. The #run command takes
a function name and an argument. mcl tries to find a function with that name
amongs the function loaded by the init and mud-specific scripts first. Then,
if that fails, it will load the file named the same as the function (e.g.
if you run the function checkConnection, mcl will try to load the file
~/.mcl/ You can use slashes here, so #run extra/test
will load ~/.mcl/extra/

The argument to the function is passed in the default variable, $_ (as is
the case with just about all embeded functions). This function runs
synchronously - mcl will not continue until you have returned from the
function, so don't use e.g. sleep() or blocking calls unless you know what
you are doing.

The other way to run Perl code is using #eval. #eval takes raw perl code,
evaluates it and prints out the result on the screen. E.g. #eval 5**5 will
calculate 5 to the 5th power and print out the result on the screen. The
full power of perl is available to you here - you could e.g. do
#eval `cat /etc/group`. Personally, I have % aliased to #run (i.e. Alias %
#run %0 in mclrc) so I can just type %`cat /etc/passwd`.

The third way is to type any command for which there also is a cmd_name
function (e.g. you type foobar, and have defined cmd_foobar, so cmd_foobar
runs. See "Custom commands" for more info).

You can also create a mcl command by creating a mclcmd_foo function. That
would make mcl react to the #foo command (# being the current command

Finally, you can use the #load command to load up a file. This works just
like the initial loading of, but you specify the filename yourself.
If you specify an absolute path, Perl will load that file. Otherwise,
~/.mcl/ will be prepended.

Scope of variables

mcl will parse all the perl code you run as one very long Perl script.
Since Perl employs garbage collection and reference counting, this is
fairly memory-efficient - things that are not used disappear.

Keep in mind however, that all variables are global unless declared local
(i.e. via my inside a function, as you should always declare such
variables - but that is basic Perl that I will not cover here).

You might want to put functions and variables that you do not want
polluting the global namespace inside a package - see the script
for an example.

Directory structure

The sample/ directory contains the standard mcl Perl script distribution.
You should copy the contents of this directory to your ~/.mcl directory.

The sys/ subdirectory contains system scripts (like sys/ that you
usually don't want to modify. These scripts will be update with new versions
of mcl.

The auto/ directory is initially empty. Files that end with *.pl there
are automatically loaded on startup. In addition, each directory has the
file named the same as itself loaded (e.g. if you have a directory called
auto/highlight, the file auto/highlight/ is loaded).

The contrib/ directory contains scripts that are not per default part of
mcl. Usually you want to move those scripts to the auto/ directory. Scripts
that consist of several parts have a directory for themselves. All the
scripts are described in the sample/contrib/README file.

Finally, the ~/.mcl directory itself can contain your own functions (or you
can put them in subdirectories).

Programming in Embedded Perl

Some things to remember:

Don't use require. It will exit mcl if it fails. Use include "" - it
will just print an error message.

If you want to print something to the screen, just print it. What happens
is that standard output is connected to a pipe which mcl reads from and
displays on the screen.

If you want to run a command, use the run function (e.g. run ("#open ar")).
This will NOT execute the command right away - it will be put on a queue
of commands to be run and that queue will be executed when your script
returns. There are a number of shortcut functions defined which makes
this easier - basically, for each mcl #function there is a mcl_function.
E.g. you can use  mcl_open("ar") instead of run("#open ar").

If you make an endless loop in your program, you're screwed.

Alt-T is handy for restarting mcl after changing some configuration or
script files.

Variables set by mcl

mcl will set a number of variables that are available to scripts. These are:

$now            Current time in seconds ($^T is when mcl started)
$mud            Name of MUD currently connected to
$VERSION        mcl version
%MUD            Information about all MUDs: hostname,port,commands
%Options        All options (e.g. $Options{mudbeep} is value of mudbeep)
%Aliases        All aliases (trigger => commands)
%Substitutions  All substitutions
%Macros         All macros

All these variables are read-only (or rather, changing any of their values
will not have any effect on mcl).

(Note that all the %hashes are not yet implemented).


Using the callout function, you can setup some of your functions to be called
occasionally. This is programmed almost entirely in Perl - mcl will call
a function called "idle" every second, and that function goes through the
list of callout functions and calls them if their time has come.

To add a function:

callout_add(\&function, period);

the period is in seconds.

To remove a function:


NOTE that the function will continue to be called until you remove it
yourself. You can add a one-shot callout by using:

callout_once(\&function, period);

If you want to pass parameters to your functions, use a closure:

    my $var = $_[0];
    callout_once( sub { my_function($var); }, period);

Custom commands

Let us say that you have implemented a module that highlights certain strings,
and you want to be able to add to those strings at runtime, rather than
having to edit the .pl file and restart mcl.

To do that you probably want to get a command hook. This is easily done this

command_add ("highlight", highlight_function);

After that, whenever the user types "highlight", your highlight_function
will be called with whatever comes after highlight in $_.

This works like aliases, so it's recursive (i.e. if you have an alias that
calls highlight it will work). NOTE: You must end the fuction by
returning '1' if you want to "stop" the command from being executed.
Otherwise, the command interpreter in mcl will continue with the command.

Commands can be similarily removed using command_remove().

There is also another, much easier way. You can just define a function
called cmd_cmdname. E.g. if you want to catch all "highlight" commands,
you can just declare a sub cmd_highlight. Unlike with hooks, mcl will
never continue to execute after your subroutine has been called.

The first way to add commands will let you remove them while they are
permanent in the second case.

Custom configuration

Custom configuration is stored in the ~/.mcl/config file. A module of yours
that wishes to save custom configuration should add a load and save hook:

load_add ("highlight", \&highlight_loader);
save_add (\&highlight_saver);

Note that you most of the time can get away with using the same function
for loading as you do for command-line adding. While the configuration
is loaded, the variable $Loading is set to 1 - you don't want to report
things too verbosely in that case.

In your save function, you should output a number of lines, all starting
with a keyword followed by space. What you put on the rest of the line is
up to you. Note that the filehandle is passed by the standard symbolic
typeglobbing method.

You can also optionally start with a comment line before writing out
your functions.

See the sys/ file for example of both this and command adding.

Remember to put your configuration keys in in lower case! The configuration
loader will look for a lower case version.

Processing multiple lines of input

Instead of using a simple input trigger, you can also hook directly to the
stream of input from the MUD. This is done using:


Once you get the input, you can do whatever you want with it. If you set
$_ to "" there, the line will not be shown at all.

Functions called by mcl

There is a number of functions that mcl will call in your perl scripts
automatically. mcl will give up after one time of calling this function and
not finding it - if you want to e.g. remove the idle function to later
return it, you will have to call enableFunction("idle") to allow mcl
to search for it again.

You probably DON'T want to register any of those functions yourself!
Use instead functions provided to ad a hook to list of functions that get
run. When nothing else is specified, the functions that add/remove a hook
are called X_add/X_remove (e.g. postinput_add). Remember to pass the function
as reference - that is either:




Note that all these functions are searched for in the sys/ directory, unless
they are defined already. 

Following functions are called:

idle            Called every second. See section about callouts longer up.

command         Ran after input has been received from the user - at the same
                level as aliased, so can be (and is) used to add custom

userinput       Called after the user has typed something on the keyboard and
                pressed enter. You can modify $_ to modify the text typed.

send            Called when about to write something to the MUD. You can
                change the text written. Note that userinput and send are
                not the same - for example "nnnn" will call userinput with
                $_ set to "nnnn" but then will call send 4 times, with 4_
                set to "n" each time.

output          Triggered on any output from the mud. Can modify it. Ran
                after triggers and substitutions.

loselink        Triggered on link loss. Typicall you would add a e.g. 5
                second calllout and try to reconnect - *unless* quit has
                been used recently. The file does exactly that.

prompt          Triggered when a new prompt arrives. By changing the prompt
                there, you can change what gets displayed in the status line.

postoutput      This is a function that is called after all output the MUD
                has been received.

init            This is called when mcl starts up. If you have somethin you
                need loaded then, put it in the auto/ directory or in the
       file - there are no hooks for this callback.

done            Called when mcl exits (including via alt-t). If you have
                started any processes, you must kill them here! (see e.g.
                the spellcheck module).

keypress        Called at every keypress done while on the input line.
                $_ holds the input line (you can modify this). $Key holds
                the value of the key pressed - you can modify that as well.

connect         Run when the user attempts to connect to a MUD                

Color codes

mcl will define a number of color codes for you that you can use in your
scripts. The full list is in sys/ You can use them in e.g. print:

print "I am ${Red}Red${Off}.\n";

Note that we use ${Red} here rather than $Red to avoid confusion where the
variable name starts and ends. $Off just resets to White on Black.

In addition to normal colors, B makes a color bold. E.g. $BRed.

To make a background color you need to use the setColor sub with the
foreground as the first argument and the background as the second - e.g.

print "You have been", &setColor($Black, $White), "KILLED!${Off}\n"

Finally, you can use the two procedures str_to_color and color_to_str to
convert colors into saveable strings. str_to color will accept a string like
"red", "bold_red", "red_blue" (red on blue background) and output the right
color code, while color_to_str will do exactly the reverse.