[Bug] CEM animation unexpected output when references used

[FFreshLX]

Description of Issue

It seems that when a part/variable references itself (to get the vanilla animation), any added expressions don't output as expected. I have used the pig as a test.

For each line of anims there are, the anim following the reference (+torad(45) in this case) is added again. The referenced vanilla anim itself is unaffected. When the anims for the part are added to that same part, it works as expected on its own (left).

Some alternatives I tried to get around it that seemed to make no difference:
-"var.leg1": "leg1.rx +torad(45)", "leg1.rx": "var.leg1"
-"var.leg1": "leg1.rx", "leg1.rx": "var.leg1 +torad(45)"

Steps to Reproduce

1. Create a CEM.
2. Add animations, including a part referencing itself like in the screenshots above.

OptiFine Version

Tested in 1.21.3 J2, 1.21.1 J1, 1.20.6 J1 pre18.
Also tested in 1.20.4 I7 where the issue doesn't occur.

Installation Method

Standalone installer used.

F3 Debug Screenshot

Additional Information

This is an issue I noticed when using Fresh Animations, as some mobs use the vanilla animations. For example the Sniffer, with which I overlay the custom anims over the vanilla keyframe anims. Or the Pillager and Piglin, where the vanilla animation is used for holding/reloading a crossbow.

[ZenithRogue]

It appears that OptiFine is evaluating the animation string as multiple times, equal to the number of lines defined, hence the +45deg every time.