Since you are overwriting the original array with the results, the simplest solution is:

s/_string$// for @list;
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Which mutates the array in-place, thus avoids constructing two lists (in and out of map) as well as 'curing' the perceived problem.

And if you wanted to create a new list from the modified values whilst retaining the original array unmodified, I'd probably do it this way also:

my @list = ...;
my @newList = @list;
s/_string$// for @newList;
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