Problem Statement

The goal is to verify the presence of a word or regular expression within several paragraphs of text (structured or not) and to format the output of the relevant paragraphs before putting them on the standard output. So here, let’s imagine that we are trying to verify the presence of a keyword "SystemError" within what I want to call "the paragraphs" "Traceback (most recent call last):" in the file Traceback.txt The expected result must be formated with ---------------- for paragraph's separator AND "Traceback (most recent call last):" as the beginning of each relevant's paragraph :

Let's start with the solution:

NB. read file, separate on blank lines
paragraphs=: ((LF,LF)&E. <;.2 ])fread 'traceback.txt'

NB. ignore text preceding 'Traceback (most recent call last)'
cleaned=:  {{y}.~{.I.'Traceback (most recent call last)'&E.y}}each paragraphs

NB. limit to paragraphs containing 'SystemError'
searched=: (#~ (1 e.'SystemError'&E.)every) cleaned

NB. add "paragraph 'separator'" and display
echo ;searched ,L:0 '----------------',LF