Index[SYMBOL] [A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] undef scalar variable undef values, elements of arrays Unicode support unless control structure else clause unquoted hash keys unshift operator until control structure unwinding hashes updating multiple files use strict pragma user input user-defined functions, subroutines |