DB<13> @a=qw/a b c/
 
  DB<14> print join ":",@a        # RIGHT
a:b:c
  DB<15> print join @a,":"        # NONSENSE  (at least in 99.9% of the cases) but no error message
:
  DB<16> # What if I REALLY want the length as delimiter?
 
  DB<17> print join scalar @a,":" # well, in <0.1% of the usecases, you can afford to be explicit
: