BRACES
Any name that starts with a letter can be used as a variable name. For instance: v, v1, v1_1, v_filename_4 To add a string immediately after a variable name can be confusing. The situation is solved by putting the variable name inside braces. Examples: $ v=im1 $ echo $v_new $ echo ${v}_new   im1_new NB: all unused variables are blank by default (generate no error)