my @chars = ('a'..'z', 'A'..'Z', 0..9);
my $plaintext_pass = do {{
  local $_ = join "" => map {$chars [rand @chars]} 1..8;
  redo unless /[a-z]/ && /[A-Z]/ && /\d/;
  $_;
}};

##</code><code>##

my @chars = ('a'..'z', 'A'..'Z', 0 .. 9);
my $plaintext_pass;
PICK: {
    $plaintext_pass = '';
    $plaintext_pass .= $chars[rand @chars] for 1..8;
    /[a-z]/ && /[A-Z]/ && /\d/ or redo PICK for $plaintext_pass;
}