sed question...

[Pollywog]

On Tuesday 25 September 2007 22:21:48 Giorgos Keramidas wrote:

>
> A word of caution there...
>
> If you plan to use GNU/Linux manpages for learning sed(1) be _very_
> cautious for GNU/Linux-specific parts.  There are subtle, yet possibly
> important differences between GNU/Linux sed and BSD sed.
>

I am generally aware that sometimes there are differences between the 
utilities used with Linux and their BSD counterparts.  As for the differences 
themselves, do they exist because someone has "reinvented" the utilities or 
is there perhaps another reason?