If you MUST sound like an IETF RFC (using cat is RECOMMENDED)

rfcify

#!/bin/sh
sed -e "s/must/MUST/" \
    -e "s/must not/MUST NOT/" \
    -e "s/required/REQUIRED/" \
    -e "s/shall/SHALL/" \
    -e "s/shall not/SHALL NOT/" \
    -e "s/should/SHOULD/" \
    -e "s/should not/SHOULD NOT/" \
    -e "s/recommended/RECOMMENDED/" \
    -e "s/may/MAY/" \
    -e "s/optional/OPTIONAL/"

grep -q "MUST" doc && 
  grep -q "SHALL" doc && 
  grep -q "SHOULD" doc &&
  grep -q "RECOMMENDED" doc && 
  grep -q "MAY" doc && 
  grep -q "OPTIONAL" doc && 
  echo BINGO

/via @grindars