Tips for golfing in Retina What general tips do you have for golfing in Retina? I'm looking for ideas that can be applied to code golf problems in general that are at least somewhat specific to Retina (e.g. "remove comments" is not an answer). Please post one tip per answer.

For reference, the online compiler is here.

@Sp3000 pointed out there is also Tips for Regex Golf. Answers here should focus specifically on Retina features and not on general regex golfing tips.
Combine loops if possible

In non-trivial computations you'll often find yourself using several loops to process data:

+`stage1
+`stage2
+`stage3


So this runs stage1 until the output converges, then stage2 until the output converges and then stage3 until the output converges.

However, it's always worth examining the stages in detail. Sometimes it's possible to run the loop in an interleaved fashion as stage1, stage2, stage3, stage1, stage2, stage3, ... instead (this depends a lot on what the stages actually do, but sometimes they make completely orthogonal changes or work well as a pipeline). In this case you can save bytes by wrapping them in a single loop:

{`stage1
stage2
}`stage3


If stage1 is the first stage or stage3 is the last stage of the program you can then even omit on of those parentheses as well (which means this can already save bytes for a loop of two stages).

A recent use of this technique can be seen in this answer.