use strict;
use warnings;

use List::Util qw{ max };
use Data::Dumper;

my %hashA = (
   11.5  => {
      1723478 => 237,
      1734789 => 114,
      1798761 => 147,
      },
   11.12 => {
      1700123 => 123,
      },
   11.01 => {
      1780345 => 456,
      },
   );

print Data::Dumper->Dumpxs( [ \ %hashA ], [ qw{ *hashA } ] );

delete $hashA{ max keys %hashA }->{ q{1734789} };

print Data::Dumper->Dumpxs( [ \ %hashA ], [ qw{ *hashA } ] );