Add an exec command

[thosakwe]

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[dumblob]

Do you mean exec of external binaries/apps or rather an "internal" exec (thus something like eval or better quoting/unquoting as proposed in #17 )?

If you meant internal one, I'd prefer the quoting/unquoting approach. But that leaves one important question open - namely how t2b can read from stdin? That's probably the last thing (along those proposed in #17) I lack in t2b - reading from stdin.