Because: 

eval {
   $t =~ tr/$search/$replace/;
};

[download]

is just normal perl code where there is no interpolation so '$' is replaced with '$' and 's' is replaced with 'r' and 'e' is replaced with 'e' and 'a' is replaced with 'p', etc. while using string eval interpolates the variables $search and $replace.

In reply to Re^4: doing tr/// on-the-fly? by jwkrahn
in thread doing tr/// on-the-fly? by Anonymous Monk

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