Preset variables

Charcoal has a few variables set to a certain value by default.

Variable	Value
θ	First input.
η	Second input.
ζ	Third input.
ε	Fourth input.
δ	Fifth input.
γ	ASCII printables.
β	Lowercase letters from a to z.
α	Uppercase letters from A to Z.
ω	The empty string.
ψ	Null byte.
χ	10.
φ	1000.
υ	An empty list.