I wrote a really witty rejoinder to this on a punchcard, but I can't seem to find a reader for it on any of my machines . . .
The problem is not that it uses whitespace, it's that the amount of whitespace has semantic meaning. Yes a Makefile uses whitespace, but so long as there's one initial tab it doesn't make any difference what amount of additional whitespace precedes the command. And I can't think of any shell where the amount of whitespace makes a syntactic difference.
No one's saying you can't use the amount of whitespace as a semantically significant portion of your programming language, but the fact that pretty much no one does any more might mean something.
Update: OOOOH, you caught me AM. Thanks for showing the one corner case that proves that Perl is just as guilty. I'll have to go delete the part where I said Perl was completely wartless itself.
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