class IO::ArgFiles is IO::CatHandle { }

This class exists for backwards compatibility reasons and provides no additional methods to IO::CatHandle, so it can be used in the same way as it, for instance, in this way:

my $argfiles = IO::ArgFiles.new(@*ARGS);
.say for $argfiles.lines;

If invoked with raku io-argfiles.raku *.raku it will print the contents of all the files with that extension in the directory. However, that is totally equivalent to:

my $argfiles = IO::CatHandle.new(@*ARGS);
.say for $argfiles.lines;

Variables

$*ARGFILES

This class is the magic behind the $*ARGFILES variable, which provides a way to iterate over files passed in to the program on the command line (i.e. elements of @*ARGS). Thus the examples above can be simplified like so:

.say for $*ARGFILES.lines;
 
# or 
while ! $*ARGFILES.eof {
    say $*ARGFILES.get;
}
 
# or 
say $*ARGFILES.slurp;

Save one of the variations above in a file, say argfiles.raku. Then create another file (named, say sonnet18.txt with the contents:

Shall I compare thee to a summer's day?

Running the command

$ raku argfiles.raku sonnet18.txt

will then give the output

Shall I compare thee to a summer's day?

As of 6.d language, $*ARGFILES inside sub MAIN is always set to $*IN, even when @*ARGS is not empty. That means that

sub MAIN () {
    .say for $*ARGFILES.lines;
}

which can be used as cat *.raku | raku argfiles-main.raku, for instance, is totally equivalent to:

sub MAIN () {
    .say for $*IN.lines;
}

and, in fact, can't be used to process the arguments in the command line, since, in this case, it would result in an usage error.

Bear in mind that the object $*ARGFILES is going to contain a handle for every argument in a command line, even if that argument is not a valid file. You can retrieve them via the .handles method.

for $*ARGFILES.handles -> $fh {
    say $fh;
}

That code will fail if any of the arguments is not the valid name of a file. You will have to deal with that case at another level, checking that @*ARGS contains valid file names, for instance.