`Devel::DProf`

        & 1b Mail::Header fold_length
        + 1b
        - 1b
        ...
        & 21 Mail::Header _fmt_line
        + 21
        & 22 Mail::Header _tag_case
        + 22
        - 22
        + 1b
        - 1b
        & 23 Mail::Header _fold_line
        + 23
        @ 0 0 4
        - 23
        - 21
        & 24 Mail::Header _insert
        + 24
        - 24
        + 21
        + 22
        - 22
        + 1b
        - 1b

& lines assign a new ID number to a subroutine
+ and - indicate that the subroutine was entered or exited
@ lines indicate that the indicated number of ticks elapsed since the last @ line