Just sets the processor spec:
{- $config{b64l} ? "#define" : "#undef" -} SIXTY_FOUR_BIT_LONG
{- $config{b64} ? "#define" : "#undef" -} SIXTY_FOUR_BIT
{- $config{b32} ? "#define" : "#undef" -} THIRTY_TWO_BIT
It only looks in ConfigData.pm at:
b32 = > 0, b64 => 1, b64l => 0