depends  gdbm   &&

optional_depends gmp '' '--without-gpm' 'Use GNU mp for bignums?' &&
optional_depends texlive '' '' 'For documentation'                &&
optional_depends readline                                         \
                 "--with-readline"                                \
                 "--without-readline"                             \
                 "Support fancy command input editing"            &&
optional_depends libffi                                           \
                 "--with-ffi"                                     \
                 "--without-ffi"                                  \
                 "Enable ffi support?"                   

.