How Do I Point a File Handle to STDOUT (or Another File Handle) In Perl?

Question

I want to make a quick script that writes to a file if a file is given, or stdout if no file is given. It would be much easier for me to do this if I could start the script by p

Answer 1

- is magic. Follow the convention or you violate the principle of least surprise.

use autodie qw(:all);
use Getopt::Long qw(GetOptions);
GetOptions(\my %opt, 'out=s') or die 'usage';
die 'usage' unless $opt{out};
open my $handle, ">$opt{out}";

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perl foo -o blahblah        # opens file blahblah for writing
perl foo -o -               # goes to STDOUT

Related: Are there reasons to ever use the two-argument form of open(...) in Perl?