ommand joins each of its arguments together with spaces after
trimming leading and trailing white-space from each of them.  If all of the
arguments are lists, this has the same effect as concatenating them
into a single list.
Arguments that are empty (after trimming) are ignored entirely.
It permits any number of arguments;
if no <I>arg</I>s are supplied, the result is an empty string.
<H3><A NAME="M5">EXAMPLES</A></H3>
Although <B>concat</B> will concatenate lists, flattening them in the process
(so giving