The source.bash rehash hook reads source.d/*.list files through a 5-element pipeline: cat | sort | uniq | sed | sed. This simplifies it to sort -u file | sed -e ... -e ...:

• cat removed: sort -u accepts filename arguments directly
• sort | uniq → sort -u: standard idiom
• Two sed invocations → one with combined expressions

Before:

for shim in $(cat "${BASH_SOURCE%/*}/source.d/"*".list" | sort | uniq | sed -e 's/#.*$//' | sed -e '/^[[:space:]]*$/d'); do

After:

for shim in $(sort -u "${BASH_SOURCE%/*}/source.d/"*".list" | sed -e 's/#.*$//' -e '/^[[:space:]]*$/d'); do

Same cleanup applied to conda.bash in #3151.

All existing tests pass.