Entered if (!\$sub_failed) {

or

Entered if (!\sub_failed) {
Entered while (<RUN>)

or

Entered if (!\$sub_failed) {
Entered while (<RUN>)
My sub-script is running...

or

Entered if (!\$sub_failed) {
Entered while (<RUN>)
My sub-script is running...
Yes, just to confirm I am running.. 

and so on...