I know that you're inquiring about matching regex's, but if all you want to do is to remove the double-quotes, you could, I think and IMHO, use the substitution regex approach as I did in the code below.

#!/usr/bin/perl

use warnings;
use strict;

my $string = '1,2,3,4,"fine","day","today"';

print "\$string = [ $string ]\n";
print "\n";

$string =~ s/\"//gx;
    
print "\$string = [ $string ]\n";
   
exit(0);
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I tried several variations using the match regex approach and couldn't get one to work. I'm sure there is a way; I just couldn't easily construct one. I'm barely regex-literate, though, so the various responses are interesting to me and have already tought me a lot that I didn't know.