The author did it in one line of Perl, using an existing library. How is that different from using awk? Yes awk is widely deployed but so is CPAN. In any case deployment isn’t part of the argument for using the UNIX philosophy.
> ... [a] more practical, much faster to implement, debug and modify solution of the problem takes only six lines of shell script by reusing standard Unix utilities.
Unlike tr, sort, uniq, awk and tr, perl is not a standard Unix utility. Not only that, but Text::LevenshteinXS is a plugin that must be downloaded.
It's still far more convenient than Knuth's work, and it follows Spinellis' reasoning about the Unix mindset, but Spinellis' Levenshtein example doesn't actually support Mcllroy's original argument.
As far as I can see, it's roughly "Data structures are hard, so let's pretend everything is ACSII text. Now we can use a really difficult systems programming language (C) to build functions with weird calling conventions ("tools") and glue them together with an awful scripting language (sh)."
'awk' fits into this framework awkwardly. It implements a restricted pattern (go line-by-line, match actions to lines), it doesn't want to be a full programming language, even though it really is.
But 'perl' is a programming language, and it wants to be one. Once you have 'perl', what is the point of using a reasonable scripting language (perl) to build functions with weird calling conventions and gluing them together with an awful scripting language? You're better off writing functions(!) with normal calling conventions (a library) and gluing them together using the good scripting language.
That logic taken taken to its conclusion replaces the shell with a clean language, encourages libraries instead of "tools", and embeds the 'awk' pattern into said language instead of relegating it to an incomplete secondary scripting language. In one word: 'scsh'.
I believe it is the idea of writing small tools focused on doing one thing well with reusability in mind as opposed to writing larger complicated tools that do multiple things.
A cargo cult philosophy never adopted by commercial UNIX clones and adored by UNIX FOSS, where the man page of each GNU tool describing the available set of command line arguments looks like a kitchen sink.
