Deparse funny keys/values in hh properly

Deparse funny keys/values in hh properly

Simply putting '...' or q(...) around a string is not sufficient to
quote it properly, allowing this sort of ‘fun’:

$ perl -l -MO=Deparse -e'BEGIN{$^H{"'\''.'\''"} = "um);\n    exit("}print'
BEGIN { $/ = "\n"; $\ = "\n"; }
sub BEGIN {
    $^H{q['.']} = "um);\n    exit(";
}
BEGIN {
    $^H{''.''} = q(um);
    exit();
}
print $_;
-e syntax OK

And B::Deparse already has a facility for quoting strings, so why
not use it?