Yes, this works! but only if I set $ENV{TEMP} within the Perl script that calls File::Temp::tempfile():

12:25 >set TEMP=.

12:25 >set TEMP
TEMP=.

12:26 >perl -T -MFile::Temp=tempfile -wE "say $ENV{TEMP}; tempfile();"
.
Error in tempfile() using template \XXXXXXXXXX: Could not create temp 
+file \JFwYM0_6Kz: Permission denied at -e line 1.

12:26 >perl -T -MFile::Temp=tempfile -wE "$ENV{TEMP} = '.'; say $ENV{T
+EMP}; tempfile();"
.

12:26 >
[download]

So, I can get the tests for MooseX::App::Cmd to pass by hacking t/basic.t like this:

SKIP: {
    my $have_TO = eval { require Test::Output; 1; };
    print STDERR $@;
    skip 'these tests require Test::Output', 5 unless $have_TO;

    local @ARGV = qw(commands);

    my $temp = $ENV{TEMP};  # ADDED
    $ENV{TEMP} = '.';       # ADDED
    my ($output) = Test::Output::output_from( sub { $cmd->run } );
    $ENV{TEMP} = $temp;     # ADDED

    for my $name (qw(commands frobulate justusage stock bark)) {
        like( $output, qr/^\s+\Q$name\E/sm, "$name plugin in listing" 
+);
    }
}
[download]

But I still don’t have a way to tweak the environment so that MooseX::App::Cmd installs “out of the box.”

Thanks for the help,