Many locales (but not the default C locale) sort this way, so if you use locale; then cmp or sort will do what you want. For example:

[am]king ~$ LC_COLLATE=hu_HU perl -we 'use locale; print join(" ", sor
+t(qw"ABU gubu abu GUBU babu Babu bubu")), "\n";'
abu ABU babu Babu bubu gubu GUBU
[am]king ~$ LC_COLLATE=hu_HU perl -we 'print join(" ", sort(qw"ABU gub
+u abu GUBU babu Babu bubu")),
"\n";'
ABU Babu GUBU abu babu bubu gubu
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