#!/bin/sh
#Join SPECIAL LINES (regexp R2) to prior REGULAR line (regrexp R1)
#Assume that file starts with REGULAR line

R1=$1
R2=$2

gsed -n '

1{/'"$R1"'/!q      	#first line must be regular. if special, quit
  h                     #populate the hold space with first line
  b}                    #fall to bottom to initiate next read

	
/'"$1"'/{              #new line is REGULAR
	x;s/\n//g;p;        #print line in hold (after removing \n, if any)
                            #current line is now in hold
	${x;p}              #special treatment if current line is last line
	b
	}


/'"$R2"'/{	    #new line is SPECIAL 
	H                   #append current line to hold space

	${x;s/\n//g;p}      #special treatment if current line is last line
}
'