I'm clutching at straws here, but if a lot of the filenames contain multiple whitespace characters, then you might get a very slight improvement doing this:

    my @f = split / /, $_, 11;
     
    # skip files that have a space or other whitespace
    # characters in their name
    next if @f > 10;
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The third parameter to split tells it not to keep looking for split points once it's found 10.