Each arg is a separate arithmetic expression to be evaluated.
let evaluates each expr in the current shell environment as an arithmetic expression using ANSI C syntax. Variables names are shell variables and they are recursively evaluated as arithmetic expressions to get numerical values. let has been made obsolete by the ((...)) syntax of ksh(1) which does not require quoting of the operators to pass them as command arguments.
ksh88 returns the following exit values:
The value of the last expression is non-zero.
The value of the last expression is zero.
ksh returns the following exit values:
The last expr evaluates to a non-zero value.
The last expr evaluates to 0 or an error occurred.
See attributes(5) for descriptions of the following attributes: