This example demonstrates how to write dplyr functions that handle both character strings and environment variables, comparing older approaches using `*_at`, `across`, and `sym` with the modern curly-curly `{{ }}` syntax. It shows the progression from string-only functions to ones supporting non-standard evaluation, using the starwars dataset to illustrate grouping and summarization. The code highlights that `{{ }}` works with bare column names but requires `sym` for strings, and that `across` handles character vectors but not environment variables.