How to loop through Jenkins multi-line string parameter?

Question

I have app_name as a multi-line string parameter, I want to loop it through so I can create ingress objects for applications.

I have defined them as below:

Now, my shell script snippet for the Jenkins file is like below:

echo "${app_name}"
            for i in "${app_name}"; do
                kubectl delete ing ${i} -n${deployment_namespace}
                cp -apvf  /tmp/flexicache-ing.yaml /tmp/flexicache-ing-${i}.yaml
                pwd
                sed -i 's/#{deployment_ns}#/'"${deployment_namespace}"'/' /tmp/flexicache-ing-${i}.yaml
                sed -i 's/#{app_name}#/'"${app_name}"'/' /tmp/flexicache-ing-${i}.yaml
                sed -i 's/#{chart_name}#/'"${app_name}"'/' /tmp/flexicache-ing-${i}.yaml
                kubectl apply -f /tmp/flexicache-ing-${i}.yaml
            done

Output:

+ echo 'flexicache-data-processor
flexicache-incident-data-processor'
flexicache-data-processor
flexicache-incident-data-processor
++ tput bold
+ bold=''
++ tput sgr0
+ normal=''
+ for i in '"${app_name}"'
+ kubectl delete ing flexicache-data-processor flexicache-incident-data-processor -nsit1-blue
Error from server (NotFound): ingresses.extensions "flexicache-data-processor" not found
Error from server (NotFound): ingresses.extensions "flexicache-incident-data-processor" not found
+ cp -apvf /tmp/flexicache-ing.yaml /tmp/flexicache-ing-flexicache-data-processor flexicache-incident-data-processor.yaml
cp: target 'flexicache-incident-data-processor.yaml' is not a directory

I have tried it with an array as well but that seems to be not working as well.

Need to understand what I am doing wrong.

P.S: Changed the code to the below:

for i in ${app_name}; do
                kubectl delete ing ${i} -n${deployment_namespace}
                cp -apvf  /tmp/flexicache-ing.yaml /tmp/flexicache-ing-${i}.yaml
                pwd
                sed -i 's/#{deployment_ns}#/'"${deployment_namespace}"'/' /tmp/flexicache-ing-${i}.yaml
                sed -i 's/#{app_name}#/'"${app_name}"'/' /tmp/flexicache-ing-${i}.yaml
                sed -i 's/#{chart_name}#/'"${app_name}"'/' /tmp/flexicache-ing-${i}.yaml
                kubectl apply -f /tmp/flexicache-ing-${i}.yaml
            done

Output is still busted:

+ sed -i 's/#{app_name}#/flexicache-data-processor
flexicache-incident-data-processor/' /tmp/flexicache-ing-flexicache-data-processor.yaml
sed: -e expression #1, char 40: unterminated `s' command

EDIT 2: I did used code of <<< before bt still not woring. Code below:

            while IFS= read -r i; do
                kubectl delete ing ${i} -n${deployment_namespace}
                cp -apvf  /tmp/flexicache-ing.yaml /tmp/flexicache-ing-${i}.yaml
                pwd
                sed -i 's/#{deployment_ns}#/'"${deployment_namespace}"'/' /tmp/flexicache-ing-${i}.yaml
                sed -i 's/#{app_name}#/'"${app_name}"'/' /tmp/flexicache-ing-${i}.yaml
                sed -i 's/#{chart_name}#/'"${app_name}"'/' /tmp/flexicache-ing-${i}.yaml
                kubectl apply -f /tmp/flexicache-ing-${i}.yaml
            done <<< "${app_name}"

Output with failed sed...

+ sed -i 's/#{chart_name}#/flexicache-data-processor
flexicache-incident-data-processor/' /tmp/flexicache-ing-flexicache-data-processor.yaml
sed: -e expression #1, char 42: unterminated `s' command

Please do not make the question "duplicate" if you have not fully understood the problem statement.