my $replace = sub {
    my $prefix = $1;

    #COLLECT YOUR PAIRS SOMEHOW; A m// OR s/// ALSO POSSIBLE
    my @pairs = split(/(.*?[=].*?)(?:[,])?/, $prefix);

    #DEAL WITH PAIRS HOWEVER YOU LIKE
    push @allpairs, @pairs;

    #RETURN WHATEVER REPLACEMENT YOU LIKE FOR $prefix
    return $prefix;  #NO CHANGE AT ALL
};

#CAPTURE EVERYTHING UP TO, NOT INCLUDING, "batch ="
$syspbuff =~ s/(.*?)(?=batch\s*=)/$replace->()/em;