libstring-compare-constanttime-perl 0.311-1build1 (arm64 binary) in ubuntu xenial

 String::Compare::ConstantTime provides one function, equals(), which takes
 two strings of the same lengh as arguments. It will return true if they are
 string-wise identical and false otherwise, just like eq. However, comparing
 any two differing strings will take a fixed amount of time, unlike eq.