If I'm correct in what it is you are looking for, you could just do this:

my $string = qq{"Hello there"};

$string =~ s/"/'/g;
[download]

That uses a simple regular expression to change every double quote to a single quote.
You could, instead of a single quote, replace it with any character you like. HTH
-Eric

Update
Ack, apparently, you have to type pretty fast or else 5 people get their answers in before you do ;-)
Would anyone care to share why perl can do tr/"/'/ faster than s/"/'/?