Unfortunately, regex syntax is not really standardized... there are many variants, which differ among other things in which "special characters" need \ and which do not. In some it's even configurable or depends on switches (as in GNU grep, which you can switch between three different regex dialects).

Hashie does not have built-in support for coercing boolean values, since Ruby does not have a built-in boolean type or standard method for coercing to a boolean. You can coerce to booleans using a custom proc.

No, there is no “glyph not found” character. Different programs use different graphic presentations. An empty narrow rectangle is a common rendering, but not the only one. It could also be a rectangle with a question mark in it or with the code number of the character, in hexadecimal, in it.

There is no standardized look/glyph, it’s up to the implementation