Raw Input

Desired Output

Paragraph-1
not this one
not this one

Paragraph-2
HERE
this one!!

Paragraph-3
this one!!
HERE

Paragraph-4
not this one

Paragraph-5
this one!!
HERE

Paragraph-2
HERE
this one!!

Paragraph-3
this one!!
HERE

Paragraph-5
this one!!
HERE

Script and Comments

Script₁

[ 1] /./!d
[ 2] :loop
[ 3] $!{
[ 4] N
[ 5] /\n$/!b loop
[ 6] }
[ 7] /HERE/!d

Comments

To get the paragraphs contains 'HERE',
- We keep all the lines of a paragraph in the pattern space.
- When the end of the paragraph reached, if it contains 'HERE', print it out; otherwise just delete it.
The end of a paragraph is reached if
- the last line of datafile is reached, or
- the newly appended line is a blank one.
Flowchart: