A generic form for a generic question:

for (@array) {
    if (condition($_)) {
        $_ = transform($_);
    }
}
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The above can also be written as

$_ = transform($_) for grep condition($_), @array;
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For example,

my @array = qw( John Jake and Jasper );
$_ = uc($_) for grep /^a/, @array;
print("@array\n");  # John Jake AND Jasper
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