my %check_dispatch = (
  2 => sub { ... }, # or better, define in named subs and, => \&check1, etc
  3 => sub { ... },
  4 => sub { ... },
  5 => sub { ... },
);

my $pw = $_;
my $index = min( (length $pw)/4, 5);
if ($check_dispatch{$index} and 'CODE' eq ref $check_dispatch{$index}) {
  die if not $check_dispatch{$index}->($pw);
}