Cleaner to do that with a number of matches:

use warnings;
use strict;
use Data::Dumper;

while (<DATA>) {
    if (/logger\s+"([^"]*)",(\w+),(.*)/s) {
        print "logger " . ('X' x length $1) . ',' . ('X' x length $2) 
+. ",$3";
    } elsif (/logger\s+([^,]*),"([^"]*)"(,?.*)/s) {
        print "logger $1," . ('X' x length $2) . "$3";
    } elsif (/logger\s+([^,]*),(\w+)(,?.*)/s) {
        print "logger $1," . ('X' x length $2) . "$3";
    }
}

__DATA__
logger abc@def,"werty^%$&"
logger ab$Łef,12trsgh
logger "765)(?>jh",hhhhhh,joebloggs
logger "7,)(?>jh",yyyyyyy,fredbloggs
[download]

Prints:

logger abc@def,XXXXXXXXX
logger ab$Łef,XXXXXXX
logger XXXXXXXXX,XXXXXX,joebloggs
logger XXXXXXXX,XXXXXXX,fredbloggs
[download]