Question

print reverse <>;
print sort <>;

What’s the exact steps perl handles with these operations?

It seems for the 1st one,perl not just reverses the order of invocation parameters,but also the contents of each file…

Answer 1

 print reverse <>;

<> is evaluated in an array context, meaning it “slurps” the file. It reads the entire file. In the case of the magic file represented by the files named in @ARGV, it will read the contents of all files in the order referenced by the command line arguments (@ARGV).

reverse then reverses the order of the array, meaning the last line from the last file comes first, and the first line from the last file comes last.

print then prints the array.

From your notes, you might want something like this:

perl -e 'sub BEGIN { @ARGV=reverse @ARGV; } print <>;' /etc/motd /etc/passwd