I want to grep through logs, and gather a certain exception stacktrace but I want to only see those that do not contain certain keywords in --after-context. I do not know in which line in after-context the keyword is.

Simple example - given this shell code:

grep -A 2 A <<EOF
A
B
C 
R
A
Z
Z
X
EOF

the output is:

A
B
C 
--
A
Z
Z

I'd like the output to be:

A
Z
Z

I want to exclude any match that has 'B' in after-context

How do I do this? Using grep is not a requirement, though I only have access to coreutils and perl.