What have you tried? We generally appreciate a show-of-effort here - see How do I post a question effectively?.

There is no way to determine the most frequent letter without counting and comparing, and brevity of source code is generally not a good goal in and of itself (unless you are golfing).

That said, one way (TIMTOWTDI) to accomplish the counting with very little code is using inline Foreach Loops and split with a hash. You can then use sort with the numerical comparison operator (<=>) to find the key with the maximum value: 

my $my_string="CCCAAAAACCCAAAAAAACCCCBBBCCAAACCBBACBBAAAAAAAAAAACAAAAA
+AAAAA";
my %count;
$count{$_}++ foreach split //, $my_string;
print Dumper \%count;
print my ($most_common) = sort {$count{$b} <=> $count{$a}} keys %count
+;

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In reply to Re: Quick way to find the letter with the most occurences in a string by kennethk
in thread Quick way to find the letter with the most occurences in a string by Anonymous Monk

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