.@ PackageName :: "SelectRuleByParam"

Rule Main
  output 'message.txt'
  param $NAME := "A"
Flow
  case $NAME
  when "A"
    $RULE := A
  when "B"
    $RULE := B
  when "C"
    $RULE := C
  end
  rule RuleSelector {R: $RULE}
End

Rule RuleSelector
  output 'message.txt'
  param $R
Flow
  rule $R
End

Rule A
  output 'message.txt'
Action
  echo "This is rule A." > {$O[1]}
End

Rule B
  output 'message.txt'
Action
  echo "This is rule B." > {$O[1]}
End

Rule C
  output 'message.txt'
Action
  echo "This is rule C." > {$O[1]}
End