<push $&var $values [$index]>
push function "pushes" (inserts) the given
$&var, at the index given by
$index (default 0).
Existing value(s), if any, are pushed to the right. The target
variable must be specified with pass-by-reference syntax -
$var - because it will be modified.
Passing it by value would not let it be modified, which might
otherwise be a silent bug - hence an error is generated if it is
passed by value.
$index value may be 0 through the number of
pre-existing values of
$var; the latter value would cause
$values to be appended to
$var. Explicit negative
$index values are interpreted as offsets from the end of
$var, e.g. -1 is the last value. Out of range or
$index values are a run-time error. An
empty-string or zero-values
$index is taken as the default,
which is 0.
push function has no implicit effect on
<$var = "a" "b" "c">
<$vals = "x" "y" "z">
<push $&var $vals 1>
After: <loop $var> $var </loop>
The output of the above example would be:
After: a x y z b c
push function is only valid in