Via the API, you can only update one campaign at a time. The only option to update multiple campaigns is the Import Campaigns option, which enables importing a delimited or Excel file of campaigns.
To Import Campaigns: Navigate to Orchestration, then click Campaigns, click the ">>" on the top right of the screen, the select "Import Campaigns..."
Ok, but the reason to use the API is exactly that, by and external page being able to modify the campaign "name": "br_" into "name":"brLatAm" over multiple campaigns inside an shared instance where I have a huge number of campaigns without the correct prefix on the name.
You need to create a simple script using PHP or your preferred language. The script process will be something like:
1. Secure Login to Eloqua
2. Search for campaigns by name or Id (depending on what you have) (API GET call)
3. Use a REGEX if needed or a simple lookup to change the campaign name (as you know all the campaigns by name and Id that you want to change, as a one off a simple lookup list is efficient)
4. Update the Campaign name in Eloqua (API PUT call)
Note: The REST API can cycle through this. Things to be careful about with "Campaign Name" in Eloqua is that they are not unique (I'm sure you know this). When updating the Campaign name the Campaign Id must be used.
You can't do this in Eloqua's landing pages. Not sure about Postman but I suspect it may not be part of their focus.
I use my tool Eloqua Admin Workbench and develop the script/API calls to do these type of changes for clients.
By the way getting a full list of Campaigns and Id is straight forward via Eloqua reporting, so you can produce a lookup list based on Id.