What does %{ $_.Key1 } mean?
%{ $_.Key1 } ⇔ ForEach-Object { Write-Output $_.Key1 } ⇔ for each object in the pipeline, echo the value of its property Key1.
% is an alias for ForEach-Object. $_ is the current object automatic variable.
%{ $_.Key1 } ⇔ ForEach-Object { Write-Output $_.Key1 } ⇔ for each object in the pipeline, echo the value of its property Key1.
% is an alias for ForEach-Object. $_ is the current object automatic variable.