As it stands, this line is a no-op, and Perl doesn't issue a warning, because it's written as method call; should be "$io->binmode();". To help Win32 users, add "$stdout->binmode();" into the same subroutine.
Thanks for the report. I've fixed it in the perl branch. Be aware that most current development is on the Rust version, a release of which will likely be coming this weekend.
Please see https://metacpan.org/release/App-Muter/source/lib/App/Muter.pm#L102
As it stands, this line is a no-op, and Perl doesn't issue a warning, because it's written as method call; should be "$io->binmode();". To help Win32 users, add "$stdout->binmode();" into the same subroutine.