[SYMBOL] [A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] object-oriented (OO) programming object-oriented programming 2nd objects 2nd clearing from memory hash data structures instance of a class representation as hashes octal (base 8) numbers open system call opening files operators arithmetic assignment binding bitwise context and file test logical conditionals and precedence of string or operator (bitwise OR) logical or control flow, using for output directing to STDOUT, STDERR and files functions for output, formatting with printf |