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)

[download]
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]

In reply to Re: tic-tac-toe regex golf by Roy Johnson
in thread tic-tac-toe regex golf by barrachois

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