I think your sort routine is missing the "->" to dereference the hash, if you're using a hashref.

If you want to use the sort approach (less efficient, as [id://dorward] noted), you can do something like that:

#!/usr/local/bin/perl
use strict;
use warnings;

my $HoA =     {'GAT' => [2, ['ttt',-3,1],['ttc',-3,3],['ccc',-1,2]],
               'AAA' => [13,['aaa',-1,2],['atg',-2,2]],
               'TTT' => [11,['tta',-2,1],['atc',-3,3]]
               };

my $key = (sort {$HoA->{$a}[0] <=> $HoA->{$b}[0]} keys %$HoA)[-1];
my $value = shift @{$HoA->{$key}}; # get the first element
print "$key $value:\n";         # Print it
for (@{$HoA->{$key}}){ # And loop through the rest
        local $,=",";
        local $\="\n";
        print @$_;
}
__END__
__OUTPUT__
AAA 13:
aaa,-1,2
atg,-2,2
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