Adds Indirection and prefix name expansion (#2102)

bash.md

@@ -183,6 +183,24 @@ base=${src##*/}   #=> "foo.cpp" (basepath)
 dir=${src%$base}  #=> "/path/to/" (dirpath)
 ```
 
+### Prefix name expansion
+
+```bash
+prefix_a=one
+prefix_b=two
+echo ${!prefix_*}  # all variables names starting with `prefix_`
+prefix_a prefix_b
+```
+
+### Indirection
+
+```bash
+name=joe
+pointer=name
+echo ${!pointer}
+joe
+```
+
 ### Substitution
 
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