#Tip29: Duplicate or Move Lines Using ':t' and ':m' Commands
##:copy :co :t (:[range]copy{address})
duplicate one or more lines from one part of the document to another.
make a copy of line 6 and put it below the current line.
Note: :t., yyp: duplicate the current line. but:
:t.: does not use register.(Command-Line Mode)
yyp: use a register.(Normal Mode)
##:move :m (:[range]move {address})
##dGp replace :'<,'>m$
d: to delete the visual selection.
G: to jump to the end of the file.
p: to paste the text that was deleted.