{: add placeholders (#17661)

pages/common/{.md

@@ -5,31 +5,31 @@
 
 - Isolate variable names:
 
-`echo ${HOME}work`
+`echo ${{{HOME}work}}`
 
 - Brace expand sequences:
 
-`echo {1..3} {a..c}{dir1,dir2,dir3}`
+`echo {{{1..3}}} {{{a..c}}}{{{dir1,dir2,dir3}}}`
 
 - Check if `variable` is set before returning text:
 
-`echo ${variable:+variable is set and contains $variable}`
+`echo ${{{variable:+variable is set and contains $variable}}}`
 
 - Set default values in case `variable` is unset:
 
-`echo ${variable:-default}`
+`echo ${{{variable:-default}}}`
 
 - Return `variable` length in characters:
 
-`echo ${#variable}`
+`echo ${{{#variable}}}`
 
 - Return a string slice:
 
-`echo ${variable:3:7}`
+`echo ${{{variable:3:7}}}`
 
 - Recursively expand a `variable`:
 
-`echo ${!variable}`
+`echo ${{{!variable}}}`
 
 - Group command output together: