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kotlinlang

Has it ever been considered to allow concatenation of `Regex`es that contain different options? A decent number of times, I've had a case where I want to build a regex that is composed mostly of constants, but with a lot of characters that would require escaping. For a very simplified example, it would be very handy if, instead of:
```Regex("""java\.lang\.ArrayIndexOutOfBoundsException: Index \d+ out of bounds for length \d+""")```
I could write:
```Regex("java.lang.ArrayIndexOutOfBoundsException: ", RegexOption.LITERAL) + Regex("""Index \d+ out of bounds for length \d+""")```

in this case you could also use:
```\Qjava.lang.ArrayIndexOutOfBoundsException:\E Index \d+ out of bounds for length \d+
```
(everything between `\Q` and `\E` is escaped)

or alternatively you could use the `Regex.escape` function, depending on your preference, like:

```Regex("""${Regex.escape("java.lang.ArrayIndexOutOfBoundsException:")} Index \d+ out of bounds for length \d+""")
```
btw, also note that the index in an out of bounds exception could also be negative, so you'd  need to account for e.g. an index of -1, unless you're specifically matching for positive indices :)

Good to know, thanks! I had forgotten to check the `Companion` page for `Regex`, and only looked at the main page.

regexes are not actually *regular* expressions, they may include named and numbered groups and back references. that makes combining them a challenge