I can't test right now on my mobile device, but something like this should presumablly work: 
while (my $line = <$IN> ) {
    $line =~ s/Weiß/Schwarz/g if /\sb\s/ .. (not /\sb\s/);

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In reply to Re: Regex with condition by Laurent_R
in thread Regex with condition by OldChamp

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