It's slightly dependant on the HL7 Version and Message Type, but assuming you're working with ORM_O01 messages using HL7 V2.3, you have a few options:

Example 1, Multiple Ifs, one for each variation (I only did 2 in the screenshot to save time) :

Example 2, If/Else where we assume that we only want "I" in OBR:18 when PV1:2 is "I", and otherwise set to "O": 

Example 3, use the $CASE function:

All of these can be combined with the response you just got here HL7 DTL formatting | InterSystems Developer Community | Business Process for the same question, assuming you want to put them into a subtransform, but I'd start with what I have shared here first, and venture into subtransforms and auxiliary-based configs after you get this nailed down. 

To give an example of where I have done something similar:

I have a Service that will check if the active mirror has changed since the last poll, and will trigger a message to the "Ens.Alert" component in the production if it has changed.

To do this, I have a service with the following code:

Class Demo.Monitoring.SystemMonitor Extends Ens.BusinessService
{

Method OnProcessInput(pInput As %RegisteredObject, Output pOutput As %RegisteredObject, ByRef pHint As %String) As %Status
{
	Set tsc = ..CheckMirroring()
	Quit tsc
}

Method CheckMirroring() As %Status
{
	Set triggered = 0

	//Get the current server
	Set CurrServer = $PIECE($SYSTEM,":")

	/**Check Global exists, and create it if it does not.(Should really only ever happen once on deployment, but this is a failsafe)**/
	Set GBLCHK = $DATA(^$GLOBAL("^zMirrorName"))
	If GBLCHK = 0{
		Set ^zMirrorName = CurrServer
		Quit $$$OK //No need to evaluate on first run
	}

	If ^zMirrorName = CurrServer {
		/*Do not Alert*/
		Quit $$$OK
	}
	Else {
		/*Alert*/
		Set AlertMessage = "The currently active server has changed since the last check, suggesting a mirror fail over."
		Set AlertMessage = AlertMessage_" The previous server was "_^zMirrorName_" and the current server is "_CurrServer_"."
		Set ^zMirrorName = CurrServer
			
		Set req=##class(Ens.AlertRequest).%New()
		Set req.SourceConfigName = "System Monitor"
		Set req.AlertText = AlertMessage
		Set req.AlertTime = $ZDATETIME($HOROLOG,3)_".000"
		
		Set tSC = ..SendRequestSync("Ens.Alert", req)
		Quit tSC
	}
}

}

Then, from within my production, I then have the service that is using this class configured with "CallInterval" set to the desired frequency of running:

Hey Gary.

I know that this has been mentioned before, but actual line breaks in the HL7 like this will likely causes issues with the parsing of the HL7 message in your receiving system.

I believe your goal should either be (see line 35):

(but maybe swapping out "/.br/" with "\X0D\\X0A\" depending on the receiving system per Jeffrey Drumm's comment here)

Or (see line 21)

Hey Thembelani.

You have a few options you can go for depending on what formats you are attempting to convert from.

You could look at something like using pandoc via the command line (as in, building an operation that does the command line calling, and then creating a set of request/response classes to call from a Process in your IRIS instance), or with with Python becoming more popular in IRIS, you could look what packages are available for doing what you're looking to do.

You could also look at libreoffice from the command line, but I found that headless libreoffice was a fair bit slower when running on Windows vs linux, so you may not get a lot of use with this approach depending on what you're running on.

There are a few options you could go for here. One would be to have your DTL go from your HL7 Message to Ens.StreamContainer, and then use a code block in your DTL to create and write the stream to store in the stream container.

Something like:

    Set stream = ##class(%Stream.GlobalBinary).%New()
    Do stream.Write(yourTextString)
    set streamContainer=##class(Ens.StreamContainer).%New(stream)

(Above is untested, and you may need to set other values within the container.)

You can then use the operation class EnsLib.File.PassthroughOperation to then write the file out to your desired location.

I have faced similar in the past, and I found the easiest way to manage this was to add a router at an early stage of the process to act as a pre-processor which makes the initial change once. Something like:

Hey Yuhong.

This would need to be achieved via the a rule as something like this:

If PV1:7.9 is then not equal to the value, then it will not hit the transform and will not then get sent to the target.

My approach would be to make use of the OAuth 2.0 Client configuration via the Management Portal.

You can configure the Issuer Endpoint here, as well as add the details of the Client, Secret, etc.

To then make use of this configuration within an Operation, you can then do something like this:

Method AuthoriseMe(Output AccessToken As %String) As %Status
{
 //Set basic parameters
 Set tSC = $$$OK
 Set myscopes = "profile"
 Set clientName = ..Client
 Set AccessToken = ""
 //Check to see if client is already authenticated
 Set isAuth=##class(%SYS.OAuth2.AccessToken).IsAuthorized(clientName,,myscopes,.accessToken,.idtoken,.responseProperties,.error)

 //If we're not authorised already, we need to authorise ourselves.
 If isAuth=0{
   //Not Authenticated - authenticate client
   //Quit on error is used here as, if we're unable to get the token 
   $$$QuitOnError(##class(%SYS.OAuth2.Authorization).GetAccessTokenClient(clientName,myscopes,,.error))
   $$$QuitOnError(##class(%SYS.OAuth2.AccessToken).IsAuthorized(clientName,,myscopes,.accessToken,.idtoken,.responseProperties,.error))
   }
 
 Set AccessToken = accessToken
 Quit tSC
}

Where ..Client is in the code snippet, the value of this will need to match the name of the client as configured in the management portal.