Change left bound behavior

[jfioasd]

• If IP goes over the left bound (not in a ? clause), the program halts.
• In a ? clause, (facing left) the IP is used as a backwards index (like the current specs). This should make for golfier IP jumps between 2 loops. (Facing right for ? clause wraps around like the current right bound specs.)
• I'll remove the condition in the ? since it's not used very often.

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• Step left 1 ({) is so common, why not make the IP start at an odd index (e.g. -1)? (this will invalidate my existing answer, change it to: ' L|qq'ol')
• Add { and } to the language. Make $ to be conditional step left. e.g. : A$BC If IP+1 is $: IP += 1 if TOS.pop is falsy.

Maybe:

• Implicitly run _ when popping from a stack without enough arguments?

Both _ and # are annoying boilerplate when writing programs.

The rest of the language is fine, I think.