The final alternation can be rewritten to save 2 keystrokes:

^(...)*(\w)\2\2|^..(\w).\3.\3|(\w)..\4..\4|(\w)...\5...\5
#becomes
^(...)*(\w)\2\2|^..(\w).\3.\3|(\w)(..\4..\4|...\4...\4)
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Then factor out the common leading dots and the trailing ..\4s to save another 6:

^(...)*(\w)\2\2|^..(\w).\3.\3|(\w)..(\4|.\4.)..\4
[download]