Tcl vs MS PowerShell

Unlike *sh Tcl has a rich standard library.

Unlike in sh you don't need to quote your variable substitutions ('"$1"').
Expanding of arguments occurs mostly explicit and if yet expected in-place (e. g. using eval or subst) it follows strict and well clear rules.
So exec test $argv would execute test with single argument.
And appending {*} before $argv would execute test with all arguments (list expansion).

With a little care you can have the same script work on Linux, *BSD, OS X and Windows.

You can expect a reasonably recent version of Tcl to either installed or available in the repositories of any popular open source *nix.

Tcl can operate at the same level of abstraction as the POSIX shell, which makes it easier to manipulate the output of other programs.

Tcl enables easy deployment through self-contained binaries known as starpacks.

Want to run something 5 times? Here you go: set i 0; time { puts done-[incr i] } 5
If you need real conditional cycle? Not a problem: for {set ready 0; set i 1} {$i <= 100 && !$ready} {incr i} { if {[exec do-some-thing] eq "ready" } {set ready 1} }
Want to measure performance of something or repeat it max 300 times and not longer than 1 seconds? Very simple: timerate { after 20 } 1000 300
How about notifying yourself when some http-server is back online? Sure thing: while {[catch { close [socket localhost 80] }]} { after 1000 }; puts "\7\7\7ONLINE!"
And you can do it also fully asynchronously using events etc.

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.

PowerShell is installable through Chocolatey.

The language can wrap and interact with code written in other language's, making it highly extensible.

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.