maybe some other flags could be added:
{E} extension of the first file
application: to reuse extension removed with {fE} & the like
current time&date flags number/ints with fixed size YYYY MM DD hh mm ss
{year}{month}{day}{hours}{min}{sec}
{timestamp}now time
application: to timestamp files
{random} a random value/int that could be stored in a scriptop stack
application: to stamp files &/or to maintain some style of session along multiple commands/scriptops
{filesize} int
{filemtime} as a timestamp int , a time_t
{fileatime} as a timestamp int , a time_t
application: to compare those attributes earlier than doing things
!! worker 4.6 added some compare option
uptnow: helper external scripts can be made each time some of those are required.
more flags are available in 5.0.0