... Related to the macro facility are the DO and FOREACH commands. ... The syntax for a DO loop is DO variable = expr1 , expr2 [ , expr3 ] { command_list 2 where the third expression is optional, defaulting to 1. The value of variable ( $variable ) is in turn set to expr1 , expr1+exp3 , ..., expr2 , and the commands in command_list executed. ... A more interesting example is the macro repeat which repeats a given macro while the given condition is true. ...