The problem is that [^\1] is interpreted as [^\001] and \001 means ascii charachter 1 in octal format.

A correct regex would be: (using look-aheads):

  m/^        # Match the start of the line
    (\w)     # Match the first letter, capture it in $1 (or \1 if you 
+re-use it in the regex)

    (        # Open capturing group for $2
      (?!\1)   # Look ahead and verify that the next charachter isn't 
+the same as the first one
      \w       # Capture a word-charachter (because of the look ahead 
+this can't be the same one as the first)
    )        # Close capture $2

    \2       # Match the second charachter another time (no need to ca
+pture this)

    (        # Open capture $3
      (?!       # Open look-ahead
         \1       # Charachter 1
        |         # Or (don't use a charachter class, else you run in 
+the same trouble as before)
         \2       # Charachter 2
      )         # Close look-ahed
      \w      # Match a word-charachter
    )       # Close capture $3
...
   /x;
[download]

I'm sure you see the pattern in this so I'm not going to go on explenaning.

The complete regex would be (tested against LOOKED and SEEMED):
m/^ (\w) ((?!\1)\w)\2 ((?!\1|\2)\w) ((?!\1|\2|\3)\w) ((?!\1|\2|\3|\4)\w) \s$/x
x-modifier is used to make the groups a little bit more visible