You don't say what problem you are having, but your regex seems to work ok for me.

Using Perl -n requires you to explicitly print the lines you want to output. I changed this to use Perl -pl to make it work. Is this the source of your problem?

c:\test>type 208336.dat
d4 f5 2 Nc3 d5 3 Bg5 c6 4 e4 fxe4 5 f3 exf3 6 Nxf3 Bg4 7 h3 Bxf3 8
Qxf3 Nf6 9 Bd3 Nbd7 10 0-0-0 Qc7 11 Rhe1 0-0-0 12 Bf4 Qb6 13
Re6 g6 14 Nb5 Ne8 15 Be2 a6 16 Qa3 g5 17 Na7+!! Qxa7 18  Rxc6+! bxc 6 
+19 Bxa6+ Qb7 20 Qa5

c:\test>perl -ple "s{\b(\d+)\b}{\1.}g" 208336.dat
d4 f5 2. Nc3 d5 3. Bg5 c6 4. e4 fxe4 5. f3 exf3 6. Nxf3 Bg4 7. h3 Bxf3
+ 8.
Qxf3 Nf6 9. Bd3 Nbd7 10. 0.-0.-0. Qc7 11. Rhe1 0.-0.-0. 12. Bf4 Qb6 13
+.
Re6 g6 14. Nb5 Ne8 15. Be2 a6 16. Qa3 g5 17. Na7+!! Qxa7 18.  Rxc6+! b
+xc 6. 19. Bxa6+ Qb7 20. Qa5

c:\test>
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