failed after 2556 iterations: at tmp/runprog.pl line 15, <$fh> line 1.

gistfile1.txt

use File::Temp qw(tempfile);

sub run_prog {
    my $cmd = shift;
    my ($tempfh, $tempfn) = tempfile(UNLINK => 1);
    my $stderr = `$cmd 2>&1 > $tempfn`;
    my $stdout = do { local $/; <$tempfh> };
    # close $tempfh; # これがないと、いずれ too many open files になる
    return ($stderr, $stdout);
}

my ($stderr, $stdout);
for my $i (1..10000) {
    ($stderr, $stdout) = run_prog("/bin/echo Hi");
    die "failed after $i iterations:$!" unless $stdout eq "Hi\n";
}