Here, I shall attempt to provide some basic documentation on what it takes to write a basic XChat Script, and then be able to test and debug it. Most of the XChat scripting I (LifeIsPain) have done is in Perl, as this interface is updated more than any other (except for the base C interface). And I just like Perl.
The XChat Technical Documents provide information on how to use the XChat interface with your scripts, they do not show how to write the scripts themselves. To write a complete XChat script, you would be best knowing how to write a generic script in that language to begin with. Even here, you won't find out how to write a Perl script (There are plenty of other sites for that, as well as Google), but how to use Perl with XChat once you already know Perl.
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