Changing the key of JSON file whilst retaining data within that bracket section

My first thought was a simple "search and replace of the underlying JSON code, inspecting it line by line. That will not work as the same "keyword" could be used in various places, but only one specific line needs to be changed.

Then I thought, read the existing data in, create a new entry, push the data into that block, and then delete the original key. The former works ... but leaves the original and all its data intact.

Here is a simplified version. (DOn't think 500+ lines would be appreciated)

{
project 1:{
     ad_campaign:{
       ad_1{
          data1,
          data2
       },
       ad_2{
         data1,
         data2
       }
     }
}
project 2:{
     ad_campaign:{
     ad_1{
        data1,
        data2
        }
     ad_201{
       data1,
       data2
       }
     }
}
}

The "data" entries are 6 lines per ad, and there could be dozens of ads per project, and dozens of projects !!

They want to change Projec1 "ad_1" to "ad_101"

As you can see, both projects have ads named "ad_1", so a simple search and replace of the underlying text code file is a no-go.

If I use $project1->{"ad_campaign"}, I can get all the data. If I then use: $project1->{"ad_campaign"}=$new_ad_id ... it creates a new section (which I =could= then copy the data line - by - line) ... but I still cannot get rid of the original "ad_1" entry! ($project1->{"ad_campaign"}->{"ad_1"} =null (no bareword allowed) / "null" / "" have no effect - even when trying to remove the internal data first. That could result in data1:'',data2:'' etc)

What I really need is a way to do $customer1->{"ad_campaign"}->{"new_ad_id"} to simply change that third key. (I've Googled "change" / "replace" JSON key, but no results ... especially as I am using PERL)

One more "spanner in the works"; the file gets saved as a single line, (Using JSON::PP The "pretty" seems to add too many spaces - tab indents would seem better) so would be difficult to break apart, and do a line by line scan anyway. (Another idea was to reiterate through file, set a flag once hit "customer1", another loop, and another flag for "ad_campaign", and then final loop seeking "ad_1". Seems a bit inefficient ... plus all the decoded data is in a hash anyway!)

Please bear in mind, I have simplified this code. Between "Project1" and "ad_campaign" could be another 50 key:value pairs PER PROJECT

There is possibly some simple solution finding / changing the value via a hash "arguement" ... but I've yet to find it!

• Somewhere else I read: delete $JSON->{"project1"}->{"ad_campaign"}->{"ad_id"} but that didn't delete the original either!

Just had a closing thought: Maybe I could do something like "indexOf" to locate project1/ad_campaign etc, and then do split/splice, pushing one half of data, then split again etc until I find the word to replace. But again, that does seem overkill for what could be a pretty basic problem