I am trying to replicate the functionality of the cat command in Unix.
I would like to avoid solutions where I explicitly read both files into variables
Since most of the other replies often get the formatting wrong (due to the piping), the safest thing to do is as follows:
add-content $YourMasterFile -value (get-content $SomeAdditionalFile)
I know you wanted to avoid reading the content of $SomeAdditionalFile into a variable, but in order to save for example your newline formatting i do not think there is proper way to do it without.
A workaround would be to loop through your $SomeAdditionalFile line by line and piping that into your $YourMasterFile. However this is overly resource intensive.