This command leaves the entire IRC network. The optional message will be displayed on any channels you are on, but *not* to those people you are querying. It is curteous to use /Quit IRC rather than just turn off the modem. To avoid irritation, you might also like to tell people you are talking to that you are going to leave.
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/Quit Be back later - X-Files
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would make everyone on the same channels as you see :