I was thinking along the same lines, but the fact that Marcello is using variables rather than constants to define the range implies that his search ranges may vary. To use tr here with differing ranges, he must use eval. As we read in perlop,

Because the transliteration table is built at compile time, neither the SEARCHLIST nor the REPLACEMENTLIST are subjected to double quote interpolation. That means that if you want to use variables, you must use an eval():

    eval "tr/$oldlist/$newlist/";
    die $@ if $@;

    eval "tr/$oldlist/$newlist/, 1" or die $@;
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HTH,

Josh