use strict;
use warnings;

use Data::Dumper;

my %x = ('period' => "2010/05", 'type' => "voice", 'tcon' => "A,B", 'hcon' => "Z,T,A" );

# extract out the value, which is a string
my $string = $x{'hcon'};

# split the string
my (@array) = split /,/,$string;

# sort the elements
my (@sorted) = sort @array;

# recreate string with sorted elements
my $new_string = join (",",@sorted);

# store back into the hash
$x{'hcon'} = $new_string;

print Dumper($x);