Often I'll want to run a shell command and capture STDOUT and STDERR separately. I wrote a function to simplify this process:

my $x    = shell_cmd($cmd);
my $exit = $x->{exit};
my $err  = $x->{stderr};
my $out  = $x->{stdout};

# Run a command and return STDOUT/STDERR/Exit
sub shell_cmd {
    use IPC::Open3;
    my ($cmd) = @_;
    my ($STDIN, $STDOUT, $STDERR, $pid, $ret) = (1,2,3,undef,{});

    # If it's an arrayref run it directly (no shell)
    if (ref($cmd) eq 'ARRAY') {
        $pid = IPC::Open3::open3($STDIN, $STDOUT, $STDERR, @$cmd);
    } else {
        $pid = IPC::Open3::open3($STDIN, $STDOUT, $STDERR, $cmd);
    }
    waitpid($pid, 0);

    # Set FH slurp mode
    local $/ = undef;

    $ret->{exit}   = int($? >> 8);
    $ret->{stderr} = readline($STDERR);
    $ret->{stdout} = readline($STDOUT);
    $ret->{cmd}    = $cmd;

    return $ret;
}