#!/bin/sh
# grep3 version c: use 'G'  instead of H

# if there is only one argument, exit

case $# in 
	1);;
	*) echo "Usage: $0 pattern";exit;;
esac;

# again - I hope the argument doesn't contain a /

sed -n '
'/$1/' !{
	# put the non-matching line in the hold buffer
	h
}
'/$1/' {
	# found a line that matches
	# add the next line to the pattern space
	N
	# exchange the previous line with the 
	# 2 in pattern space
	x
	# now add the two lines back
	G
	# and print it.
	p
	# add the three hyphens as a marker
	a\
---
	# remove first 2 lines
	s/.*\n.*\n\(.*\)$/\1/
	# and place in the hold buffer for next time
	h
}'