Kilroy Washere

DISCLAIMER: As always, or almost so anyways, I don't claim to hold the correct interpretation to any work, especially concerning H., perhaps Tool's most ambiguous song. All I offer is food for thought, or, worst-case-scenario, a wasted four minutes of your life. Sue me.

"What's coming through is alive."
I'm starting off on a roll -- I have no clue what this line means.
"What's holding up is a mirror."
...Not yet.
"But what's singing songs is a snake. Looking turn this piss wine."
Ok. I think this song is a beautiful account of a man's battle to remain moral. He's given a choice between an obvious right and wrong. On one side he sees a snake (evidently a universal tempter) who offers an alluring proposition i.e. to turn his wrongdoings into satisfaction.
As for the mirror line: This represents a type of conscience which I, of no scientific merit, proclaim there to be several forms of. I believe people judge the morality of their acts either by assessing consequence, feeling empathy, or (in this case) reflecting on their self-image. The mirror represents a realistic conscience; not an angel on his shoulder, but rather, a reminder of how this choice may atrophy his own self-image. This mirror currently is, and typically does hold it's ground against the voice of desire.
"They're both totally void of hate, But killing me just the same."
Now, I really love this line. It levels the ground between the perceived malevolent and the idealized saint. Neither is out for ruin. The snake wants you to do the wrong, not because it's wrong, but because it will make you feel good in some way. Likewise, the mirror urges you toward redemption, not in accord with some angelic morality, but simply because it will make you feel good in another way. Nevertheless, it is the combined individual who must suffer the weighted task of choosing, and the inevitable consequences to ensue.

This concludes my pretentious opinion, a million and one ways fallible. Sue me.