Description

A block begins with a line of the form section N begin and ends with a line of the form section N end where N is a number.

We want to get every block containing `this'.

Raw Input

Desired Output

.....
section 1 start
 line 1-1
section 1 end
....
section 2 start
 line 2-1
 line 2-2 this!
section 2 end
....
....
section 3 start
 line 3-1 this!
section 3 end
....
section 4 start
section 4 end
....

section 2 start
 line 2-1
 line 2-2 this!
section 2 end
section 3 start
 line 3-1 this!
section 3 end

Script and Comments

Script₁ [ 1] /^section [0-9][0-9]* start$/!d [ 2] :loop [ 3] N [ 4] /\nsection [0-9][0-9]* end$/!b loop [ 5] /this/!d
Comments Every line not belonging to any block will be discard by Step [1]. Once the first line of a block has been read by Step [1], the loop consisting of Steps [2] thru [4] will append all lines of the block to the Pattern Space. After all lines of a block have been read to the Pattern Space, Step [5] will delete them if that block does not contain `this'.