See perlrecharclass, perluniprops. 
$ perl -e'print "hello" =~ /\p{Lowercase}+/'
1

$ perl -e'print "HELLO" =~ /\p{Uppercase}+/'
1

$ perl -e'print "Hello" =~ /\p{Uppercase}\p{Lowercase}+/'
1

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In reply to Re: How to use \l and \u in regex mathing patterns? by Anonymous Monk
in thread How to use \l and \u in regex mathing patterns? by pat_mc

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