#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my $VAR = {
   "diameterCreditControlRecord" => {
       "dAFirstValueAfter" => "+1920.57",
       "originHost" => "aaa://lg-2;transport=tcp",

       ..... snip .....

       "callingPartyNumber" => "\241\b\30dB\205",
       "accumulatorValue4" => 0,
       "accumulatorDeltaValue" => 11043,
       "subscriberID" => "\241\b\30dB\205",

       ..... snip .....
   }
};

my $t = $$VAR{diameterCreditControlRecord};

# Now just convert each field you care about into a hex string:
$$t{$_} = tohex($$t{$_}) for (qw(
        callingPartyNumber subscriberID
));

print Dumper($VAR);

sub tohex {
.....
}