method
use
use(k=nil, v=true)
private
Used internally by the keep and discard methods
use() # marks the entire flash as used
use('msg') # marks the "msg" entry as used
use(nil, false) # marks the entire flash as unused (keeps it around for one more action)
use('msg', false) # marks the "msg" entry as unused (keeps it around for one more action)

