You want to sort the whole row as a string, then sort on the first column numerically, correct?

#!/usr/bin/perl -w
use strict;

my @sorted = map {$_->[0]} sort {
    $a->[0] cmp $b->[0] ||
    $b->[1] <=> $a->[1]
} map {[ $_ ,/(\w+)\s+(\w+)\s+(\w+)/]} <DATA>   ;
print  for @sorted;
    

__END__
2 4 a
1 9 b
6 8 a
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UPDATED

My mistake- I thought you were asking a perl perlfunc:sort question, rather than Gnu sort. (I also didn't realize that this was a mid-thread revision of the subj. line .). For a perl question, then you would be looking for...

my @sorted = map {$_->[0]} sort {
    $a->[3] cmp $b->[3] || # sorted ascending alpha on col 3
    $b->[2] <=> $a->[2]    # then sorted reverse num on col 2
} map {[ $_ ,/(\w+)\s+(\w+)\s+(\w+)/]} <DATA>   ;

print  for @sorted;
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