perl sort array / list使用逗号或点进行字符串连接

I have:

#!c:\Dwimperl\perl\bin\perl.exe

use strict;
use warnings;

# define an array
my @letters = ('b', 'c', 'a', 'e', 'd');
print sort @letters , "\n";
#!c:\Dwimperl\perl\bin\perl.exe

use