I+used+to+when+a+boy

"I used to when a boy" what does this mean? In the last line of the thrid stanza Emily Dickinson states a kind of odd sentence that doesn't seem to be correct. We know that Emily Dickinson is a woman, but are we sure that she is speaking from the position of a woman? She could be speaking from the position of a boy.

True, I think she's trying out a boy's perspective. Also very interesting in that stanza is Dickinson referencing the dead person as It, not He or She.