scripting hardstatus with backtick

[TJ Harrell]

I'd like to have a hardstatus similar to this:

hardstatus alwayslastline "%{Bw}%l%= "

I would like to modify this somewhat, so that the color is changed when the
current load exceeds 1.5.
I could easily output a string like:

"%{Bw}0.19, 0.11, 0.07%= "

from a perl script, but screen will not interpret the string escapes
contained in the output of a script when used from backtick. Also, I would
prefer to be more extensible, and actually pass information from screen to
the script like so:

backtick 1 0 0 /home/system/stat %l

Neither of these work correctly when tried. Is there any way to do both of
these that I'm missing?

Thanks,
TJ Harrell