# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(?i)(?:\[|\()(?:M|F|T|MF|FM|\?)(?:\d+)?(?:M|F|T|MF|FM|\?)?(?:\d+)?(?:\]|\))//gm;t' <<< "[F]
(F)
[M]
(M)
[T]
(T)
[FM]
[MF]
(FM)
(MF)
[F44]
(f45)
[F44M50]
[M21F31]
(F44M50)
(M21F31)"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html