my %h_prefixed;
my %h_numbers;

while(my ($key, $val) = each %h) {
    $h_numbers{$key} = $val if looks_like_a_number($val);
    $h_prefixed{$key} = "p$val";
}

##</code><code>##

my %h_prefixed;
@h_prefixed{keys %h} = map "p$_", values %h;