bash-3.00$ uname -a
HP-UX td176 B.11.23 U ia64 1928826293 unlimited-user license
bash-3.00$ seq 3 | sed ':b; N; $!bb; s/\n//g'
bash: seq: command not found
sed: The label :b; N; $!bb; s/\n//g is greater than eight characters.
bash-3.00$ echo -e '1\n2\n3\n' | sed ':b; N; $!bb; s/\n//g'
sed: The label :b; N; $!bb; s/\n//g is greater than eight characters.
bash-3.00$ 


$ uname
NetBSD
$ seq 3 | sed ':b; N; $!bb; s/\n//g'
sed: 1: ":b; N; $!bb; s/\n//g": unused label 'b; N; $!bb; s/\n//g'
1
2
3
$