help with text

Hi,
does anyone knows how can I do this with commands like sed or tr?
Input File:
this
is
the
text
Output file
t h i s
i s
t h e
t e x t

Thanks!!!!

something to start with:
sed 's/./ & /g;s/^ //;s/ $//' file

ruby -ne'print split("")*" "' file

Or in perl

perl -ne '$a=join(" ",split(//)); print $a;' file