When comparing MS PowerShell vs Rebol, the Slant community recommends Rebol for most people. In the question“What is the best programming language to learn first?” Rebol is ranked 49th while MS PowerShell is ranked 55th. The most important reason people chose Rebol is:
Almost natural language, for example: `write %out.html read http://google.com`.
Ranked in these QuestionsQuestion Ranking
Pro Helpful Help
The help system is designed to evolve over time; running
update-help downloads the latest content.
When searching for help on items, you can simply type
help commandname to get information about a command.
If you're not sure what you're looking for, but have a rough idea, you can search on partial command names, or even specify specific verbs to get a list of commands potentially of interest; e.g.
help -verb write.
The information in help gives a good overview of the commands you're looking at, along with code examples, so you can see real-world usage without resorting to the web.
When calling a method with multiple parameters, rather than passing one variable per parameter you're able to "splat" one variable to the method, with the parameters taking their values from its properties.
Commands can be chained via the pipeline, allowing output from one to be cleanly fed as input to the next.
Pro Chocolatey Package
PowerShell is installable through Chocolatey.
The language can wrap and interact with code written in other language's, making it highly extensible.
Pro Multi-Platform (ish)
Though Windows Powershell only works on Windows, the open source implementation Pash (http://pash.sourceforge.net/) allows the same language to be run on other OSes.
Pro Human friendly
Almost natural language, for example:
write %out.html read http://google.com.
Code is data, and data can be code. Rebol is based on a simple block data structure, used both for data and for the code itself. Blocks can be manipulated programmatically, and then evaluated as code. This makes metaprogramming easy in Rebol.
Pro Graphical user interface
Beginners are usually stuck making command-line applications in other languages, because GUIs are too hard. Rebol GUIs are easy enough to start with.
Pro Very simple syntax
Rebol's name came from "Relative Expression Based Object Language". Rebol is a functional language and everything is an expression that returns a value. Things that have to be baked into the grammar in other languages are simple function calls with block arguments in Rebol.
Pro Domain specific languages
Rebol's simple homoiconic syntax makes it easy to create "Rebol dialects"--domain-specific languages optimized for a particular purpose. The Rebol distribution includes many of these, and users are free to create more. These DSLs make tasks that would be complicated to express in other languages easy.
Con Very verbose
The commands themselves, as well as the output and error messages, are VERY verbose
Con No separators
A function call expression has no parentheses, and there are no separators between sequenced expressions, not even newlines. This means that you have to know the arity of every function in an expression to know how to parse it. It also means you can run into subtle, hard-to-find bugs if you don't provide enough arguments, since the result of the next expression will be passed instead.
Con Not (yet?) Free Software
Rebol 2's core is free (gratis) for commercial use, but the license prohibits modification, a violation of the DFSG. Rebol 3 is Free Software (Apache 2.0), but isn't production ready.