[General meaning in software]
[much used in Tcl]
In Tcl, to enhance a core command (or existing proc) by renaming the command to be enhanced, then creating a procedure with the same name as the core command that provides the desired functionality.
Easy example, provided by RS:
rename exit _exit proc exit {{code 0}} { set fp [open test a] puts $fp "trapped exit at [clock format [clock seconds]]" _exit $code }
[General case needs uplevel ...]