my %Orig=('a b'=>44,  'c d'=>22, rr=>99);

my %Copy = map {my $y=$Orig{$_}; #Save Copy of Val
                tr/ /_/;
                $_ => $y}
             keys %Orig;

print qq(C: $_ => $Copy{$_}\n) for keys %Copy;
print qq(O: $_ => $Orig{$_}\n) for keys %Orig;