I actually learned this the hard way when porting some Perl written on Windows to Linux. I had no problem useing something with incorrect case, but actually relying on the class name caused things to break! This was a long time ago with ActiveState Perl. I wonder if they ever fixed that? I don't have a Windows box to test that on.

use FOO; # but finds Foo.pm
my $foo = FOO->new; # but told me I didn't load the FOO package!
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