I'm kind of new to scripting Xchat with python. But this is a simple "On Join" script for Xchat.

__module_name__ = "AnaBotNowYourGone's On Join Script For Xchat" 
__module_version__ = "Script Version 1.0" 
__module_description__ = "An on join sort of script for xchat"

print "\0034",__module_name__, __module_version__,__module_description__,"!\003"

import xchat

def on_join(word, word_eol, userdata):
      triggernick, triggerchannel, triggerhost = word
      destination = xchat.get_context()
      destination.command("say Hi " + triggernick + " and welcome to this channel! This channel is called " + triggerchannel + " Enjoy your stay!")

xchat.hook_print('Join', on_join)