Forum Invaders by guedesacp

#!usr/bin/env perl

use warnings;
use strict;
use feature 'say';

sub toupper{
    my $w = shift;
    $w = chr $w;
    $w =~ tr/[a-z]/[A-Z]/;
    $w = ord $w;
    return $w;
}

sub isalpha{
    my $char = shift;
    $char = chr $char;
    return 1 if ($char =~ /[a-zA-Z]/) or return 0;
}

sub strtochar{
    my $c = shift;
    my @b = split (//, $c);
    for (my $i = 0; $i < @b; $i++){
        $b[$i] = ord $b[$i];
    }
    return @b;
}

sub encode{
    my @word = strtochar($_[0]);
    my @key = strtochar($_[1]);

    my ($a, $tword);

    for ($a = 0; $a < @word; $a++){

        if(isalpha($word[$a]), isalpha($key[$a])){

            $word[$a] = toupper($word[$a]) - 65;
            $key[$a] = toupper($key[$a]);

            my $cript = $key[$a] + $word[$a];

            if ($cript >= 91){
                $cript -= 26;
            }

            $word[$a] = $cript;
            $tword .= chr $word[$a];
        }
    }
    return $tword;

}

sub decode{
    my @word = strtochar($_[0]);
    my @key = strtochar($_[1]);

    my ($a, $tword);

    for ($a = 0; $a < @word; $a++){

        if(isalpha($word[$a]), isalpha($key[$a])){

            $word[$a] = toupper($word[$a]);
            $key[$a] = toupper($key[$a]);

            my $cript =  $word[$a] - $key[$a] +65;

            if ($cript <= 64){
                $cript += 26;
            }

            $word[$a] = $cript;
            $tword .= chr $word[$a];
        }
    }
    return $tword;
}

sub help{
    print "\n[+] Cifra de Vigenere\n";
    print "[0] Coder => guedes.acp\n\t\treleitura de MMxM";
    print "\n\tModo de uso: $0 <palavra> <chave> <e|d>\n";
    print "\n\t \"A chave e a palavra devem ter o mesmo tamanho\"\n\n";
    exit(0);
}

sub main{
    my $cmd;
    if(@ARGV != 3){
        help;
    }

    if(length($ARGV[0]) != length($ARGV[1])){
        help;
    }
    {
        if ($ARGV[2] eq 'd'){
            $cmd = decode($ARGV[0], $ARGV[1]);
        }
        elsif ($ARGV[2] eq 'e'){
            $cmd = encode($ARGV[0], $ARGV[1]);
        }
        else {
            help;
        }
    }

    print "PALAVRA: " . $ARGV[0] . "\n";
    print "CHAVE: " . $ARGV[1] . "\n";
    print "RESULTADO: " . $cmd . "\n\n";
}

main;