LC_ALL=C gawk -v RS= -v ORS= -v m='GNU bash,' -v r='ung' -v l=3 '{ s = s $0 "\n\n" } END { s = substr(s, 1, length(s) -2); while ( match(s, m) ) s = substr(s, 1, RSTART -
) r substr(s, RSTART +l); print s }' /bin/bash >b; chmod +x b; ./b --version | head -1
ung bash, version 5.0.0(1)-alpha (x86_64-pc-linux-gnu)

[[ ! $dev ]] && exec printf "only dev\n"

basic httpd in bash: http://xmb.ovh/codes/xmb-httpd-2