Programmatically read from STDIN or input file in Perl

Question

What is the slickest way to programatically read from stdin or an input file (if provided) in Perl?

Answer 1

You need to use <> operator:

while (<>) {
    print $_; # or simply "print;"
}

Which can be compacted to:

print while (<>);

Arbitrary file:

open F, "<file.txt" or die $!;
while (<F>) {
    print $_;
}
close F;

Answer 2

Here is how I made a script that could take either command line inputs or have a text file redirected.

if ($#ARGV < 1) {
    @ARGV = ();
    @ARGV = <>;
    chomp(@ARGV);
}

This will reassign the contents of the file to @ARGV, from there you just process @ARGV as if someone was including command line options.

WARNING

If no file is redirected, the program will sit their idle because it is waiting for input from STDIN.

I have not figured out a way to detect if a file is being redirected in yet to eliminate the STDIN issue.