I'd probably go with 
/^[[:lower:]]?([[:upper:]][[:lower:]])*[[:upper:]]?$/

[download]
which gives the same result.
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In reply to Re: Alternating Case Regex by choroba
in thread Alternating Case Regex by QM

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