just.sh

#!/usr/bin/env bash
sed --version | head -1

printf "%s\n%s" "$1" "$2" | gsed -r '
x;N
G
s/\n/!@/
:
/@\n/bZ
s/-!(.*)@ /\1 !@/
s/!(.*[- ])(@.*1)$/\1!\2/
s/@(.)(.*)1$/\1@\2/
s/-!(.*-)(@.*)\n$/\1!\2\n1/
s/(\n!@) /\1/
s/-!(.* )(@.*)\n$/\1!\2\n1/
s/-!(.*-)(@.*1)$/\1!\21/
s/!(.*)-@([^ ]) /\1\2!@ /
t
s/ !@(.*)\n$/\n!@\1#/
s/!(.*-)@(.*)\n$/\1\n!@\2#/
s/!(.*)(@ | @)(.*)\n$/\1\n!@\3#/
s/-!(.*[^-])@([^ ]) (.*)\n$/\1\2\n!@\3#/
s/!(.+)@([^ ].*)\n$/\n!@\1\2#/
/#|!@.*\n$/{s/#|\n$//;G;b}
:Z
s/-?!|@.*//g
s/ \n/\n/g
s/^/%/
:B
G
/%.*\n.+\n/!bQ
:C
s/%([^\n])(.*)1$/\1%\2/
tC
s/([^\n]+)%\n/%\1\n/
:D
s/%([^ \n]* )(.*)1$/\1 %\2/
tD
s/(^|\n)([^\n]+)%(.*1)$/\1%\2\3/
tD
s/%([^\n]*)\n(.*)\n$/\1\n%\2/
tB
:Q
s/%(.*)\n1*$/\1/'

out.txt

$ ./just.sh 111111 'Hello, world!'
sed (GNU sed) 4.2.2
Hello,
world