From The Camel, section 29.2.87 local

You can use local to give temporary values to individual elements of arrays and hashes, even lexically scoped ones:

if ($protected) {
    local $SIG{INT} = 'IGNORE';
    precious();     # no interrupts during this function
}                   # previous handler (if any) restored
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The example is not lexically scoped but the note applies to your situation, as I found when I wrote this test:

my @foo = (0..9);
print "[1] ", join('|', @foo), "\n";
local $foo[3] = 100;
print "[2] ", join('|', @foo), "\n";
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I learn something new here every day ...