Another way:

...
my @seq;

# read past the header
while(<IN>){
   last if /^Sequences producing/;
}

# assuming remaining data is fixed
while(<IN>){
   chomp;
   next if /^\s*$/;

   # capture the score
   /^.{67}\s*(\d+)/;

   # push anonymous array - [score,line] 
   push @seq, [$1,$_];
}
close IN;

print join $/,
       (  map  { $_->[1] }               # print original line
          sort { $b->[0] <=> $a->[0] }   # sorted by score
          @seq
       )[0..9];                          # top ten
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