e quote are evaluated and replaced. Note that
in IOS.sh, double quotes are NOT deleted when evaluating an
expression, in order to be compatible with prior IOS CLIs.

Second, there are single quotes. Any character within a single quote
string is left as it is. So, the traditional meanings of single
quotes, '$', and the other special characters are not available within
a single quote string. If it is desired to put a single quote within a
single quoted string, the single string must first be terminated, and
then the an escaped single quote must be entered, followed by another
single quote to continue the quote sequence. 
 Router>echo 'foo'\''bar'
 foo'bar
Notice that the quotes are deleted after used. Only the escaped single
quote remains.

Third, there are backquotes. Backquotes have a special meaning in the
IOS.sh. They will take anything within the backquote, and execute as
if it were typed on the command line. The output of this command then
replaces the backquoted string, and IOS.sh interprets it as if it were
typed by the user. THis is a bit confusing, so here is an example.

 Router#`echo dir`
 `echo dir`
 Directory of system:/

     2  -r--           0                    <no date>  default-running-config
     1  -rw-        1583                    <no date>  running-config
     3  dr-x           0                    <no date>  vfiles

 No space information available

The backquote `echo dir` echos 'dir', which is then executed as if it
had been typed. This can be used in almost any place that text can be
typed. The main exception is that it doesn't work within single
quotes.