chomp(my @unsorted = (<DATA>));
my @sorted = sort { $a cmp $b } @unsorted;
say for @sorted;

__DATA__
1208782,abc
406744,def
367455,abc
283191,mps
226159,abc
197688,rxwz
137875,rxwz
115901,abc
107297,def
99213,mps

##</code><code>##

use Data::Dump qw(pp);

chomp(my @lines = (<DATA>));
my $sums = {};
for my $line (@lines)
{
   my ($num,$let) = split ',', $line;
   $sums->{$let} += $num;
}
say pp($sums);