Question

I created two subs one to do Fibonacci and the other to test even numbers. When I call it though it is saying my for loop in line 7 the sub Fibonacci is illegal why?

#!/usr/bin/perl
use strict;
use warnings;


my ($x,$y);
my $num = 0;

sub Fibs($start,$stop){
    for ($start..$stop){
        ($x, $y) = ($y, $x+$y);
            my $total += $y;
        }
    print "$total \n"
}

sub even($num){
    if ($num % 2 == 0){
        return $num;}
}

my $big_total = Fibs(even($num), 3999999)

Edited from suggestions below.

Clearly I am missing something. From feedback updated to new version.

#!/usr/bin/perl
use strict;
use warnings;


my ($x,$y);
my $num = 0;

sub Fibs{
    my ($start, $stop) = @_ ;
    for ($start..$stop){
        my ($x, $y) = (0,2);
            if ($x % 2 == 0){
                ($x, $y) = ($y, $x+$y);
                    my $total += $y;
        }
}

my $big_total = Fibs(0, 3999999)

Answer 1

In addition to the missing opening braces, Perl doesn’t support that kind of declaration for subroutine parameters.

Rather than

sub Fibs($start, $stop) {
    ...
}

you need to write something like:

sub Fibs {
    my($start, $stop) = @_;
    ...
}

(Perl does have prototypes, but they’re not really intended for declaring the types of parameters, and they don’t provide names. See this article for a discussion.)

Other problems:

You should add

use strict;
use warnings;

You never use the $x and $y that you declare in the outer scope.

Your even function appears to be incomplete. It doesn’t (explicitly) return a value if its argument is an odd number. What exactly is it intended to do?