Synopsis:
   $shift(<variable name>)
   $unshift(<variable name> <word> [<word> ...])

Technical:
   These functions are used to add or remove words to or from the beginning
   of a variable.  The $shift() function removes the first word (and any
   space padding) from the beginning of the variable and returns the word.
   The $unshift() function prepends the given string to the variable, and
   returns the resultant string.

   Note that the variable name itself must be used, without any leading
   '$' character.

Practical:
   These functions are more efficient means of adding or removing data to
   or from a variable than assigning the variable's value to itself.  They
   are identical to the SHIFT and UNSHIFT commands, except that they also
   have return values.

Returns:
   shift:   word "shifted" off of the variable
   unshift: resultant string after function call

Examples:
   $unshift(foo blah)             prepends "blah" to $foo
   $shift(foo)                    removes "blah" from $foo and returns it
   $unshift(foo bar  booya)       prepends "bar  booya" to $foo

See Also:
   pop(6); push(6); shift(5); unshift(5)