Nice, so far the only other solution that beats the original :-)

                Rate BillKSmith2 choroba2 LanX2 choroba1 LanX1 haukex1
+ BillKSmith1 orig tybalt89 haukex2
BillKSmith2  38227/s          --     -55%  -60%     -72%  -72%    -83%
+        -85% -85%     -87%    -88%
choroba2     85658/s        124%       --  -10%     -38%  -38%    -62%
+        -66% -67%     -70%    -74%
LanX2        95639/s        150%      12%    --     -31%  -31%    -57%
+        -62% -63%     -67%    -71%
choroba1    138099/s        261%      61%   44%       --   -1%    -38%
+        -44% -47%     -52%    -58%
LanX1       138866/s        263%      62%   45%       1%    --    -38%
+        -44% -47%     -52%    -58%
haukex1     223763/s        485%     161%  134%      62%   61%      --
+        -10% -14%     -22%    -33%
BillKSmith1 248507/s        550%     190%  160%      80%   79%     11%
+          --  -5%     -13%    -25%
orig        260650/s        582%     204%  173%      89%   88%     16%
+          5%   --      -9%    -21%
tybalt89    287084/s        651%     235%  200%     108%  107%     28%
+         16%  10%       --    -13%
haukex2     331543/s        767%     287%  247%     140%  139%     48%
+         33%  27%      15%      --
[download]

Out of curiosity, I tried tr/// instead of regex, much faster :)

sub validatetr {
  local $_ = shift;
  length >= 20              ? 1 :
    !tr/a-z// || !tr/A-Z//  ? 0 :
    length >= 16            ? 1 :
    !tr/0-9//               ? 0 :
    length >= 12            ? 1 :
    !tr/a-zA-Z0-9//c        ? 0 :
    length >= 8             ? 1 :
    0;
  }
[download]

Out of curiosity, I tried tr/// instead of regex, much faster :)

Looks like it's a winner :-)

                Rate BillKSmith2 choroba2 LanX2 choroba1 LanX1 haukex1
+ BillKSmith1 orig tybalt89 haukex2 tybalt89_2
BillKSmith2  40957/s          --     -53%  -58%     -71%  -71%    -82%
+        -84% -85%     -85%    -88%       -91%
choroba2     88071/s        115%       --  -10%     -38%  -38%    -61%
+        -65% -67%     -69%    -73%       -82%
LanX2        97356/s        138%      11%    --     -31%  -31%    -57%
+        -61% -63%     -65%    -71%       -80%
choroba1    141499/s        245%      61%   45%       --    0%    -37%
+        -44% -47%     -50%    -57%       -70%
LanX1       141499/s        245%      61%   45%       0%    --    -37%
+        -44% -47%     -50%    -57%       -70%
haukex1     225463/s        450%     156%  132%      59%   59%      --
+        -11% -15%     -20%    -32%       -53%
BillKSmith1 252057/s        515%     186%  159%      78%   78%     12%
+          --  -5%     -11%    -24%       -47%
orig        265476/s        548%     201%  173%      88%   88%     18%
+          5%   --      -6%    -20%       -44%
tybalt89    281788/s        588%     220%  189%      99%   99%     25%
+         12%   6%       --    -15%       -41%
haukex2     331918/s        710%     277%  241%     135%  135%     47%
+         32%  25%      18%      --       -30%
tybalt89_2  476665/s       1064%     441%  390%     237%  237%    111%
+         89%  80%      69%     44%         --
[download]

Read more... Benchmark code (13 kB)