[tjnycum@nx1 Data]$ 3dcalc -a EPI_All_Runs_mean+orig. -expr 0 -prefix blank+orig.BRIK.gz
++ 3dcalc: AFNI version=AFNI_2009_12_31_1431 (Feb 25 2010) [64-bit]
++ Authored by: A cast of thousands
*+ WARNING: input 'a' is not used in the expression
++ Output dataset ./blank+orig.BRIK.gz+orig.BRIK

I made sure that message is accurately reporting what it's doing. It is.

Just in case I was forgetting a quirk I'd usually remember, I went ahead and tried a couple different versions one might conceivably consider to be a "prefix" with '.gz' (even though they'd be inconsistent with the other AFNI binaries).... :-p

[tjnycum@nx1 Data]$ rm blank+orig.BRIK.gz+orig.*
[tjnycum@nx1 Data]$ 3dcalc -a EPI_All_Runs_mean+orig. -expr 0 -prefix blank.BRIK.gz
++ 3dcalc: AFNI version=AFNI_2009_12_31_1431 (Feb 25 2010) [64-bit]
++ Authored by: A cast of thousands
*+ WARNING: input 'a' is not used in the expression
++ Output dataset ./blank.BRIK.gz+orig.BRIK
[tjnycum@nx1 Data]$ rm blank.BRIK.gz+orig.*
[tjnycum@nx1 Data]$ 3dcalc -a EPI_All_Runs_mean+orig. -expr 0 -prefix blank.gz
++ 3dcalc: AFNI version=AFNI_2009_12_31_1431 (Feb 25 2010) [64-bit]
++ Authored by: A cast of thousands
*+ WARNING: input 'a' is not used in the expression
++ Output dataset ./blank.gz+orig.BRIK

Is this a regression?

Danke