#! /usr/bin/perl

# sum

# add up elements of array
sub sum {
    for ($i = 0; $i < @_; $i++) {
        # $s is the sum of the first $i array elements
        # $s == $_[$0] + .. + $_[$i-1]
        $s = $s + $_[$i];
    }
    return $s;
}

# main program

@a1 = (2, 4, 6, 8);
print "The sum of elements in @a1 is ", sum(@a1), "\n";