use 5.010;
use strict;
use warnings;

my $string = "(1,2,3) XXX (1,2,3)";
my $open = -1;  
$open = index $string, "(", $open + 1 for 1 .. 2; 
my $close = index $string, ")", $open + 1; 

substr($string, $open + 1, $close - $open - 1) =~ s/(\d+)/'$1'/g; 
say $string;

__END__
(1,2,3) XXX ('1','2','3')