osx man page for lassign

lassign(n)						       Tcl Built-In Commands							lassign(n)

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NAME
       lassign - Assign list elements to variables

SYNOPSIS
       lassign list varName ?varName ...?
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DESCRIPTION
       This command treats the value list as a list and assigns successive elements from that list to the variables given by the varName arguments
       in order.  If there are more variable names than list elements, the remaining variables are set to the empty string.   If  there  are  more
       list elements than variables, a list of unassigned elements is returned.

EXAMPLES
       An illustration of how multiple assignment works, and what happens when there are either too few or too many elements.
	      lassign {a b c} x y z	  ;# Empty return
	      puts $x			  ;# Prints "a"
	      puts $y			  ;# Prints "b"
	      puts $z			  ;# Prints "c"

	      lassign {d e} x y z	  ;# Empty return
	      puts $x			  ;# Prints "d"
	      puts $y			  ;# Prints "e"
	      puts $z			  ;# Prints ""

	      lassign {f g h i} x y	  ;# Returns "h i"
	      puts $x			  ;# Prints "f"
	      puts $y			  ;# Prints "g"
       The lassign command has other uses.  It can be used to create the analogue of the "shift" command in many shell languages like this:
	      set ::argv [lassign $::argv argumentToReadOff]

SEE ALSO
       lindex(n), list(n), lset(n), set(n)

KEYWORDS
       assign, element, list, multiple, set, variable

Tcl									8.5								lassign(n)