addinput

 What: addinput
 Where: ftp://ftp.tcl.tk/pub/tcl/mirror/ftp.procplace.com/sorted/packages-7.6/devel/addinput-3.6b.gz 
 Description: Implements two new Tk file handle callback commands.
 Updated: 10/1998
 Contact: mailto:[email protected]  (Mark Diekhans)

DKF: I vaguely remember reading that this was the origin of fileevent, which became part of Tcl with 7.6…