So I’ve sort-of figured out how to do conditional blocks. The following LaTeX initially appears to work:

newboolean{cond1}
newboolean{cond2}

setboolean{cond1}{false}
setboolean{cond2}{true}

ifthenelse{boolean{cond1}}
{
A block of conditional text in here.
blah blah
}

ifthenelse{boolean{cond2}}
{
A separate block of conditional text in here.
blah blah
}

I say initially appears to work, because it works fine for the first 4 or 5 attempts, but then some combination of blocks (begin{verbatim} for example), causes it to break on the 6 attempt. If I include a verbatim block in that 6 attempt, latex outputs an obscure error message… something along the lines of:

Runaway argument?
some code here end {verbatim} end {listing}
! Paragraph ended before @xverbatim was complete.

Which is rather infuriating, considering that I’ve got verbatim blocks in the previous conditional sections (it doesn’t complain about those), and because I’ve almost got the answer to my problem.