> Some of it I recognize as being an artefact of the time, when conciseness really mattered

It was an artefact of bursting out of those constraints, but honoring them still. The roots of perl as a “more capable, less restrictive” sed/awk means that it must support `perl -pi.bak -e oneliner file`, just like sed did — and so from that core requirement forward, everything it did, does. By the heyday of Perl5 era, conciseness was not a requirement, but the sed-compat roots remained a focus of the language’s creator.