c:\@Work\Perl\monks\OldChamp>perl -wMstrict -e
"use 5.010;
 ;;
 my $t = do { local $/;  <>; };
 print qq{[[$t]] \n\n};
 ;;
 my $pre  = qr{ \S+ \s \S+ \s }xms;
 my $post = qr{ \s [^\n]+ \n [^\{]* \{ }xms;
 ;;
 $t =~ s{ ^ $pre b $post \K Weiss \b }
        {Schwarz}xmsg;
 ;;
 print qq{<<$t>> \n\n};
"  1148125.dat
[[..........
[FEN "1B3k2/2R1b3/4p1pp/2r1P1p1/6P1/7P/5PK1/8 w - - 4 34"]
{Weiss am Zug}  *

..........
[FEN "1B6/1Q4bk/R5p1/1pp4p/8/1n5P/1P4PK/1q6 b - - 2 42"]
{Weiss am Zug}  *

...........
[FEN "1Bn4r/1k3q2/1pp1bbp1/1N1p1p1r/Q2Pp3/6PN/PP2PPB1/K1R4R b - - 0 23"]
{Weiss am Zug}  *

...........
[FEN "1K6/4kp2/1P4p1/7p/7P/1r3PP1/1p6/1R6 w - - 3 52"]
{Weiss am Zug}  *

]]

<<..........
[FEN "1B3k2/2R1b3/4p1pp/2r1P1p1/6P1/7P/5PK1/8 w - - 4 34"]
{Weiss am Zug}  *

..........
[FEN "1B6/1Q4bk/R5p1/1pp4p/8/1n5P/1P4PK/1q6 b - - 2 42"]
{Schwarz am Zug}  *

...........
[FEN "1Bn4r/1k3q2/1pp1bbp1/1N1p1p1r/Q2Pp3/6PN/PP2PPB1/K1R4R b - - 0 23"]
{Schwarz am Zug}  *

...........
[FEN "1K6/4kp2/1P4p1/7p/7P/1r3PP1/1p6/1R6 w - - 3 52"]
{Weiss am Zug}  *

>>