Undefine
We may need to undefine variables or function definitions to release them from memory. For details please check undef.
$ undef all;
$ x=1;
$ undef(`x, VAR);
$ x=1; y=2;
$ undef(`x`y, VAR);
$ share table(1..3 as x, 4..6 as y) as t;
$ undef(`t, SHARED);
$ def f(a){return a+1};
$ undef(`f, DEF);
$ a=1; b=2;
$ undef all, VAR;