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.