No need to put things in order... just harness the powers of .. and a literal hash slice:

my %hash = qw( 100 g 101 j 102 d 103 h 104 t 105 a );

my $number = 3;
my $start  = 101;
delete @hash{$start .. $start+$number-1};
[download]

enjoy!

--
Casey
   I am a superhero.