shift, unshift
Synopsis:
unshift
shift <variable name>
Description:
unshift prepends the given word (or words) to the given variable, padded
with a single space. The variable name itself may not contain a leading '$';
the command uses the variable itself, not the expanded contents. If the variable
does not exist, it is created containing the given word(s) (just as if assign
were used).
Aliases:
shift is the exact opposite of unshift, in that it chops off the
first word in the variable. If there is only one word in the variable, the variable
is deleted. Both unshift and shift are functionally equivalent
to the $unshift() and $shift() functions, respectively.