Sample reproducer environment:

"""
# cat > input.file<<EOF
a
b
c
d
EOF

# for i in $(cat input.<TAB>
"""

  In rhel 7 it would correct complete 'input.file'.

  In rhel 8 it just bells and does not auto complete. It works if adding a backslash before the dollar sign, for example:

# for i in \$(cat input.<TAB>

or if adding a newline:

# for f in
$(cat input.<TAB>

  The easiest workaround is to not let it generate an autocompletion for 'for', and have in .bashrc or similar file the command:

complete -o default for

but this is just working around what appears to be a bug, as when spawning the subshell to generate the auto completion, it is actually attempting to autocomplete the string '$(cat input.' instead of 'input.'

Another possible workaround, but really brute force would be to have:

shopt -u progcomp

in some initialization file, but that would not really bring compatibility with rhel7 behavior. Still, it would work usages of:

$(cat input.

other than just as a 'for' argument.