Without this, errors would go unreported: further steps within the for
loop would be performed, and all source versions would be attempted. If
one is lucky, a general issue (missing backslash somewhere) could easily
be spotted as it would affect all source versions. In worse cases, a
failure somewhere in the middle could go unnoticed.

Therefore: use “set -e” locally, and print an explicit error message
when any failure happens; also break out of the loop to ensure the first
issue is fixed before considering other items.