Andrew,

Yeah, I thought about it and it's almost certainly not a problem. Since you're using bash, I think that what will happen is that a string of the form "foo[12]" (quoted here for clarity; quotes in the shell would stop this behavior) will be replaced by "foo1" or "foo2" or (more problematically) "foo1 foo2" (interpreted by the shell as two separate words) if and only if these files exist in the current path. Since you're unlikely to have files named "something+tlrc1" or "something+tlrc.HEAD1" lying around, you shouldn't need to escape numeric subbrik indices at all. (Symbolic subbrik indices like "pain#0_Coef" still need to be escaped because of the '#' character.)

Isaac