There are subjective elements to readability, but is not entirely so. We can convey more with code in general than the traditional syntax (which is meant to be line based and contained in strings) allow. SREs allow the structure of the code to convey information about the regular expressions they represent. Subparts of a compound expression can be presented on separate lines and commented, etc. It feels like moving from line editing to screen editing.

 

Another benefit to SRE, at least as they're implemented scsh, is the interpolation of scheme values into larger SREs. SREs can be created independently and combined. They can be combined with program input (with all the power and danger of that). These things can be more clearly written than they could be with the traditional RE strings, where you'd be concating strings or using a language's string interpolation facilities (which might not map 100% to a consistent RE interpolation). I haven't had time to look at the full srfi document to see if this feature or something like it has been preserved.

In general, it seems to me the big benefit is clarity. Traditional RE string syntax has a high floor to understandability, and even experts have to parse out complicated ones into subparts to get them. Why not present the parts independently and optionally document them?

-Roderic