You use parenthesis in PowerShell to control an execution order. However, some language keywords are not legal inside parenthesis, like try and catch. See what happens with these two lines:
try { 1 } catch { 2 } (try { 1 } catch { 2 })
The second line will fail with an exception. To work around this, you can use $() instead:
$(try { 1 } catch { 2 })
With $(), you can group commands without the language restrictions that () imposes.
