Hello basiliscos,

The “fat comma” operator, =>, stringifies its left-hand operand, so the Perl compiler sees a string and not a function, i.e. my @x = map { 'rand', rand } (0 .. 5). But with parentheses, the expression rand() is evaluated before the => operator, so it is the function’s return value that is stringified.

See perlop#Comma-Operator.

Hope that helps,