Why does だけ come before は?


In [a song](https://www.youtube.com/watch?v=opADNvgeZYY) I was listening to,
there was the sentence:

> 僕はＥ缶だけは最後までとっておく

With the given translation:

> I will only take the E-Tank at the very last moment.

I don't understand why だけ comes before は, since は seems to apply to Ｅ缶. It
seems strange to me, I would expect: Ｅ缶は, i.e. _I'm going to say something
about Ｅ缶_. Which is the case in the song. But with Ｅ缶だけは it seems like
something is said about "only E-can". i.e. "I will take only the E-can at the
end", instead of "I will take the E-can only at the end". Where the thing that
"only" applies to changes.

Why does だけ come between は and the noun? Is this perhaps something that is
done to make the song sound better?




> 僕はＥ缶だけは最後までとっておく

means:

> I'll spare at least E-Tanks until the last moment.  
>  I will use anything but E-Tanks before the last moment.

This だけ refers to E-Tanks, not "at the last moment" part. とっておく means "to
spare / keep", not "to take / bring".

To be clear, he's not saying he's going to throw away items other than
E-Tanks. Obviously it doesn't make sense :)

だけは and だけ are different:

>   * これだけ読みなさい。 Read only this. (Don't read others.)
>   * これだけは読みなさい。 Read at least this.
>   * このゲームだけ欲しい。 I only want this game. (I'm not interested in other games)
>   * このゲームだけは欲しい。 At least I want this game. (although I also want others)
>




> 僕はＥ缶だけは最後までとっておく

means:

> I'll spare at least E-Tanks until the last moment.  
>  I will use anything but E-Tanks before the last moment.

This だけ refers to E-Tanks, not "at the last moment" part. とっておく means "to
spare / keep", not "to take / bring".

To be clear, he's not saying he's going to throw away items other than
E-Tanks. Obviously it doesn't make sense :)

だけは and だけ are different:

>   * これだけ読みなさい。 Read only this. (Don't read others.)
>   * これだけは読みなさい。 Read at least this.
>   * このゲームだけ欲しい。 I only want this game. (I'm not interested in other games)
>   * このゲームだけは欲しい。 At least I want this game. (although I also want others)
>

