The right way to do this is simply to use 'foreach'. Eg to replace every occurence of 'cat' with 'dog':

foreach (@strings) {
  s/cat/dog/g;
}
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A common error is to use 'map':

map { s/cat/dog/g; } @strings;
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The point of map is that it returns a copy of the transformed list. If you don't want a new list, but just want to transform the list 'in place', use foreach.