Правила деления на 7 задача

use strict;
use warnings;
 
sub seven {
    my ($n) = (@_);
    my $count_times = 1;
 
    my $last_digit = int(reverse($n)/10**(length_digits($n)-1));
    $n = int($n/10) - (2 * $last_digit);
    print "N>$n\n";
 
    while ($n > 7) { # я думаю, что проблема тут и он не выходит когда надо
        $count_times++;
        $last_digit = int(reverse($n)/10**(length_digits($n)-1));
        $n = int($n/10) - (2 * $last_digit);
        print ">$n\n";
    }
    print "Count_times = $count_times\n";
    ($n, $count_times);
}
 
 
sub length_digits {
    my ($n) = (@_);
    my $count_digits = 0;
    
    while ($n != 0) {
        $count_digits++;
        $n = int ($n/10);
    }
    $count_digits;
}

# Кол-во цифр в числе $number
my $count = length $number
 
# взять $n чисел слева в числе $number
my $from_left = substr( $number, 0, $n )
 
# взять $n чисел справа в числе $number
my $from_right = substr( $number, -$n )

#!/usr/bin/perl
use strict;
use warnings;
 
# Function to check divisibility by 7
sub is_divisible_by_7 {
    my ($num) = @_;
 
    # Make sure the number is positive
    $num = abs($num);
    
    # Check the divisibility by 7 rule
    while ($num >= 10) {
        my $last_digit = $num % 10;
        $num = int($num / 10);
        $num -= 2 * $last_digit;
    }
 
    # If the number is divisible by 7 or becomes 0, it's divisible by 7
    return $num % 7 == 0;
}
 
# Main program
print "Enter a number: ";
my $number = <STDIN>;
chomp($number);
 
if (is_divisible_by_7($number)) {
    print "$number is divisible by 7.\n";
} else {
    print "$number is not divisible by 7.\n";
}