Note that a question mark after a quantifier ({2}?) does not mean optional, but rather non-greedy. You need to put parens around the sub-expression to make it optional:

/^(\d{6}\.?(?:\d{2})?\w?$/;
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If the optionals aren't independent, you may need to nest them:

/^(\d{6}    #leading digits
  (?:\.?    #if dot, then
   (?:(?:\d{2})? #if two digits, then
    \w?)))$/x;   #maybe a character
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Note the use of anchors, to prevent matching part of the name.