You can use local, though that only works for individual variables, not an entire package:

$Data::Dumper::blah = 0;
say $Data::Dumper::blah; # 0
{
    local $Data::Dumper::blah = 1;
    say $Data::Dumper::blah; # 1
}
say $Data::Dumper::blah; # 0
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The nice thing about local variables is that they're dynamically-scoped, so if you invoke subroutines from that block, they will also see the localized value.