How do I specify "the word under the cursor" on VIM's commandline?

Question

I want to write a command that specifies "the word under the cursor" in VIM. For instance, let's say I have the cursor on a word and I make it appear twice. For instance, if the word is "abc" and I want "abcabc" then I could type:

:s/\(abc\)/\1\1/ 

But then I'd like to be able to move the cursor to "def" and use the same command to change it to "defdef":

:s/\(def\)/\1\1/ 

How can I write the command in the commandline so that it does this?

:s/\(*whatever is under the commandline*\)/\1\1 

Answer 1

While in command-line mode, CTRL+R CTRL+W will insert the word under the cursor.

See the help for c_CTRL-R for a listing of all the other special registers:

:help c_CTRL-R