Software :: Replace Newline Pattern In File By Other Newline Pattern In A Shell Script?

I have several (vhdl) files containing a pattern with newline characters that I need to replace by another pattern that also contains newline characters.

I start with something like:

Code:

I want to replace it by something like:

Code:

(I need to paste some lines)

As I need to do this (very) often I want to use a shell script.

I tried:

1.

Code:

result:

Code:

2.

Code:

result:

File remains unchanged

3.

Code:

result:

Code:

4.

Code:

result:

Displays the unchanged testfile

How I can automate the pattern replacement?

Code: