deferex.nim

proc example =
  defer: echo "deferred"
  raise newException(ValueError, "an exception")

example()

deferex2.nim

proc example =
  defer: echo "deferred"
  try:
    raise newException(ValueError, "an exception")
  except ValueError:
    echo "caught exception: " & getCurrentExceptionMsg()

example()

output.txt

# ./deferex
deferred
deferex.nim(5)           deferex
deferex.nim(3)           example
Error: unhandled exception: an exception [ValueError]

# ./deferex2
caught exception: an exception
deferred