using ls has some advantages.

That's why some use glob.

Doing it in pure Perl requires several lines

It would take more than 7 lines to do the equivalent of or die $! when using cat. It's so complex you probably don't even bother doing it.

The OP's code is the perfect example. By using cat,

• he used three lines instead of two,
• he removed the error checking he'd do with open,
• he introduced a lot of overhead in a loop,
• he introduced a bug that deletes trailing blank lines, and
• he introduced a bug for files with spaces and other special characters in their names.

Update: Added OP as an example.