[AUCTeX] inserting dollars

[juan mari alberdi]

Hello,

In section 4.1 of the manual is said,

'... The first `$' you insert in a paragraph will do nothing special.  
The second `$' will match the first.  This will be indicated by moving 
the cursor temporarily over the first dollar sign... '

That works with me.
The following one, however, doesn't,

'... If you enter a dollar sign that matches a double dollar sign `$$' 
AUCTeX will
automatically insert two dollar signs.  If you enter a second dollar 
sign that matches a single dollar sign, the single dollar sign will 
automatically be converted to a double dollar sign...'

Juan Alberdi