$ cat -vet working.txt
H$
 after 1 space$
  after 2 spaces$
no leading spaces$
text^I^Ifollowed by 2 tabs$
target for^Ireplace1$
...$
source for^Ireplace1$
...$
^LH$
 after 1 space$
  after 2 spaces$
no leading spaces$
text^I^Ifollowed by 2 tabs$
target for^Ireplace2$
...$
source for^Ireplace2$
...$
^LH$
 after 1 space$
  after 2 spaces$
no leading spaces$
text^I^Ifollowed by 2 tabs$
target for^Ireplace3$
...$
source for^Ireplace3$
...$