"Less is more"—Mies van der Rohe
Postmodernism:
"Less is a bore"—Robert Venturi
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Guided by these famous quotes, if I were to call a programming language a "Modernist" language, I'd think of something that prizes elegance. It can't just be a small language, it has to be a small language with a few features powerful enough to actually do more.
I would think of languages like Scheme or Smalltalk or C as fitting that label. But not JavaScript or Java or C++.
And if I were to call a language "Postmodernist," I'd expect a language to incorporate historical motifs, whimsey/surprise, and arresting/attention-grabbing features.
Perl might fit that bill. C++ manages to be "more" without being postmodernist, IMO.