[MacPerl] tr question

[Nobumi Iyanaga]

Hello,

I have a short question about the "tr" command.  Is it impossible to use 
variables in the tr command, in this way? :

$str = "aiueokakikukeko";
$to_find = "aiueo";
$replace_with = "hijkl";
$str =~ tr/$to_find/$replace_with/;
print $str, "\n";

Thank you in advance for any comments!

Best regards,

Nobumi Iyanaga
Tokyo,
Japan