how to pipe the output of pcompos as input for pflip

Dear list,

I can use two separate commands to crop and flip an .hdr image:

pcompos -x 800 -y 800 ./sky.hdr -100 0 > ./sky_clipped.hdr
pflip -h ./sky_clipped.hdr > ./sky_flipped.hdr

However, I don't seem to be able to "pipe" the output of pcompos as input
for pflip using the following script:
pcompos -x 800 -y 800 ./sky.hdr -100 0 | pflip -h > ./sky_flipped.hdr

I'm sure I missed something here, so please kindly advise!

Thanks a lot!

- Ji