Oil: http://www.oilshell.org/release/latest/doc/command-vs-expression-mode.html

elvish: Prefix syntax for arithmetic. So there's only one mode? Code can get lispy because () is command substitution.

Oh Syntax Comparison|https://htmlpreview.github.io/?https://raw.githubusercontent.com/michaelmacinnis/oh/master/doc/comparison.html

The shell language for single commands is almost identical, but the rest is homoiconic syntax? There is a math command for infix, e.g. math '1.2 + 3.4'.

NGS Manual|https://ilyash.github.io/ngs-doc/ngslang.1.html

Switching between syntaxes

In command syntax it is possible to switch to code syntax in one of the following ways:

• Simple switching (for a lack of better name)
• Single argument substitution switch
• Multiple arguments substitution switch

In code syntax it is possible to switch to command syntax in one of the following ways:

• Capture switch
• Capture and parse switch
• Command switch

Mash Shell Quick Reference|http://mash-shell.org/quick-reference-guide/

Mish is a sublanguage within Mash for launching processes, with a similar syntax to a traditional shell.

By default, Mash is in "regular Mash" mode. If a command line starts or ends with !, the entire line is interpreted as a Mish command. If ! is issued by itself as a command, then Mash toggles into Mish by default, and the prompt changes from a $ to a !.

Neugram Shell|https://github.com/neugram/ng/blob/master/docs/shell.md (Go-based, implemented in Go)

A $$ ... $$ expression in Neugram is a sequence of shell commands. If used as a top-level statement in the interpreter, commands are executed as they are parsed. Otherwise, shell commands are executed when the $$-expression is evaluated according to standard Neugram rules.