If you are using DBI to access MySQL then something like this may be better.

use DBI;

my $dbh=DBI->connect('DSN info here');

my $string="D'ith";

my $val_to_put_in_mysql=$dbh->quote($string);
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Or if you are using placeholders in your query then DBI will do the quote on insert for you. Either way DBI will fetch it back as D'ith for you.