Name
undef
Synopsis
undef expr
Undefines the value of
expr, which must be an lvalue. Use only
on a scalar value, an entire array or hash, or a subroutine name
(using the & prefix). Any
storage associated with the object will be recovered for reuse
(though not returned to the system, for most versions of Unix).
The undef function will
probably not do what you expect on most special variables. The
function always returns the undefined value. This is useful
because you can omit the expr, in which
case nothing gets undefined, but you still get an undefined value
that you could, for instance, return from a subroutine to indicate
an error.
You may use undef as a
placeholder on the left side of a list assignment, in which case
the corresponding value from the right side is simply discarded.
Apart from that, you may not use undef as an lvalue.
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