Comment décrypter le hachage stocké par bcrypt

j'ai ce script qui crypte un mot de passe mais je ne sais pas comment l'inverser et le décrypter. Cela peut être une réponse très simple mais je ne comprends pas comment le faire.

#!/usr/bin/perl
use Crypt::Eksblowfish::Bcrypt;
use Crypt::Random;

$password = 'bigtest';
$encrypted = encrypt_password($password);
print "$password is encrypted as $encryptedn";

print "Yes the password is $passwordn" if check_password($password, $encrypted);
print "No the password is not smalltestn" if !check_password('smalltest', $encrypted);

# Encrypt a password 
sub encrypt_password {
    my $password = shift;

    # Generate a salt if one is not passed
    my $salt = shift || salt(); 

    # Set the cost to 8 and append a NUL
    my $settings = 'a$'.$salt;

    # Encrypt it
    return Crypt::Eksblowfish::Bcrypt::bcrypt($password, $settings);
}

# Check if the passwords match
sub check_password {
    my ($plain_password, $hashed_password) = @_;

    # Regex to extract the salt
    if ($hashed_password =~ m!^$2a$d{2}$([A-Za-z0-9+.]{22})!) {
        return encrypt_password($plain_password, ) eq $hashed_password;
    } else {
        return 0;
    }
}

# Return a random salt
sub salt {
    return Crypt::Eksblowfish::Bcrypt::en_base64(Crypt::Random::makerandom_octet(Length=>16));
}