This is an optional suggestion. It must be explicitly enabled with a directive enable=require-variable-braces in a # shellcheck comment or .shellcheckrc

partial_path='example'

curl "http://example.com/$partial_path_version/explain.html"

partial_path='example'

curl "http://example.com/${partial_path}_version/explain.html"

If a variable gets called, and there is a string that gets appended to the variable that could get misinterpreted as possibly part of the name of the variable. Then it will not call the right variable.

• StackOverflow: How do we separate variables from letters in shell scripting