Though for the sake of readability I'd rather go for a hash of boundaries.

you may also want to limit the max length of your password.

 
use strict;
use warnings;
use Data::Dump qw/pp dd/;
use List::Util qw/min/;



sub pw_not_ok {
    my $pw  = shift;

    my $short     =
      sub { "is too short" };

    my $lowercase =
      sub { /[a-z]/ ? "" : "has no lowercase character" };

    my $uppercase =
      sub { /[A-Z]/ ? "" : "has no uppercase character" };  ### UPDATE
+D

    my $number =
      sub { /[0-9]/ ? "" : "has no number" };

    my $special =
      sub {
          if (
              /[\x21-\x2F]/ ||
              /[\x3A-\x40]/ ||
              /[\x5B-\x60]/ ||
              /[\x7B-\x7E]/
             ) {
              return "";
          } else {
              return "has no special characters";
          }
      };

    my $pass = sub {""};



    my %rules_by_max_length =
      (
       7 =>  [ $short ],
       11 => [ $lowercase, $uppercase, $number ,$special ],
       15 => [ $lowercase, $uppercase, $number           ],
       19 => [ $lowercase, $uppercase                    ],
       50 => [ $pass ]
      );

    my $len = length $pw;

    return "too long" if $len >= 50;

    my @boundaries = sort { $a <=> $b } keys %rules_by_max_length;

    for my $boundary ( @boundaries ) {
        next if $len > $boundary;
        my $rules = $rules_by_max_length{$boundary};

        for my $rule ( @$rules ) {
            $_ = $pw;
            if ( my $err = $rule->() ) {
                return $err;
            }
        }
    }
    return;
}

# --------- Tests

for my $pw (
            "A" x 3 ,
            "A" x 7 ,
            "A" x 11,
            "a" x 5 . "A" x 3,
            "a" x 5 . "A" x 3 . "1",
            "a" x 5 . "A" x 3 . "1" .":",
            "a" x 24,
            "a" x 100,
           ){
    if ( my $err = pw_not_ok($pw) ){
        warn "ERROR: $pw is $err\n";
    } else {
        print "OK: $pw\n"
    }
}
[download]

ERROR: AAA is is too short
ERROR: AAAAAAA is is too short
ERROR: AAAAAAAAAAA is has no lowercase character
ERROR: aaaaaAAA is has no number
ERROR: aaaaaAAA1 is has no special characters
ERROR: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa is too long
OK: aaaaaAAA1:
OK: aaaaaaaaaaaaaaaaaaaaaaaa
[download]

UPDATE

see Re^6: Efficient way to verify scalar contents