`regexp` feature uses the pcre2 library to enable the user to define
regular expressions for matching text and applying text formatting to
the matches. An example from the theme configuration I used to test
this:
[terminal.themes.win95.text_format_regexps]
"listing.subject" = { "\\[[^\\]]*\\]" = { attrs = "Bold" } }
"listing.from" = { "\\<[^\\>]*\\>(?:(?:\\s*$)|(?=,))" = { attrs = "Italics" } }
[terminal.themes.win95.text_format_regexps."pager.envelope.body"]
"^>.*$" = { attrs = "Italics" }
"\\d+\\s?(?:(?:[KkMmTtGg]?[Bb])|(?:[KkMmTtGg][Bb]?)(?=\\s))" = { attrs = "Bold | Underline" }