Separate stdout and stderr in `run`

[fearphage]

Introduces new variables: $output_stdout, $output_stderr, $lines_stdout, $lines_stderr Existing $output and $lines variables remain.

I found this while looking into #55 and noticed it never made it into a PR.

@duggan Thanks for the excellent contribution. I hope you don't mind.

@ahippo Was previously tagged in the branch as well.

Any thoughts on merging this @sstephenson? There was already a good bit of discussion about the topic in #55.

This is not my code. I'm just making a PR for code that I believe adds the feature that I would like. I see it cannot be merged cleanly. I wouldn't mind cleaning it up to get it merged. Let me know.

[ahippo]

I found this while looking into #55 and noticed it never made it into a PR.

@duggan Thanks for the excellent contribution. I hope you don't mind.

@ahippo Was previously tagged in the branch as well.

Any thoughts on merging this @sstephenson? There was already a good bit of discussion about the topic in #55.

This is not my code. I'm just making a PR for code that I believe adds the feature that I would like. I see it cannot be merged cleanly. I wouldn't mind cleaning it up to get it merged. Let me know

Yeah, it would be great to have this merged! There is some tricky code though. I can also help if needed.