Convert .opus and .m4a files to .mp3

to_mp3.pl

#!/usr/bin/env perl

use v5.28;
use warnings;
use Path::Tiny;
use String::ShellQuote;

my $dir = path(shift // '..');

# Convert the .opus files by piping to opusdec first.
# This creates a WAV, which sox will convert to MP3.
#
for my $path ($dir->children(qr/\.opus\z/)) {
    say $path;

    my $infile = shell_quote $path;
    # say $infile;

    my $outfile = $path->basename =~ s/\.opus$/.mp3/r;
    # say $outfile;

    my @cmd = ('sox', "|opusdec --force-wav $infile -",  $outfile);
    system(@cmd) == 0 or die "system '@cmd' failed: $?";
}

# Convert the .m4a files with ffmpeg and LAME.
#
for my $path ($dir->children(qr/\.m4a\z/)) {
    say $path;

    my $infile = shell_quote $path;
    # say $infile;

    my $outfile = shell_quote($path->basename =~ s/\.m4a$/.mp3/r);
    # say $outfile;

    my $cmd = "ffmpeg -v 5 -y -i $infile -acodec libmp3lame -ac 2 -ab 192k $outfile";

    system($cmd) == 0
        or die "system '$cmd' failed: $?";
}