my @unsorted = qw(
                864278_864377
                864518_864703
                851171_851270
                855398_855579
                856258_856357
                861015_861139
                866387_866549
                791806_792296
               1088806_1082296
);

##</code><code>##

use Data::Dumper;
print Dumper(\@sorted);