You can break the universe of expressions up into four types:
Simple expressions consist of a single literal or variable.
Simple expressions with side effects -- A side effect is when a variable's value is changed by the expression. Side effects can be caused using any of the unary operators: +, -, ++, -. These operators have the effect of changing the value of a variable just by the evaluation of the expression.No other Perl operators have this effect-other than the assignment operators, of course. Function calls can also have side effects- especially if local variables were not used and changes were made to global variables.
$numPages++; # Increments a variable ++$numPages; # Increments a variable chop($firstVar); # Changes the value of # $firstVar-a global variable
Simple expressions with operators are expressions that include one operator and two operands. Any of Perl's binary operators can be used in this type of expression.
10 + $firstVar; # Adds ten to $firstVar $firstVar . "AAA"; # Concatenates $firstVar and "AAA" "ABC" x 5; # Repeats "ABC" five times
A complex expression can use any number of literals, variables, operators, and functions in any sequence.
(10 + 2) + 20 / (5 ** 2); 20 - (($numPages - 1) * 2); (($numPages++ / numChapters) * (1.5 / log(10)) + 6);