<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="ServiceId.suffix" value="_TEST" />
  </appSettings>
</configuration>

my $searchStr2 = "value=\".*\"";
my $suffix2 = "scheisse";
my $replaceStr2 = "value=\"_" . $suffix2 . "\"";
replaceInFile("f:\\tmp\\myfile.config",$searchStr2,$replaceStr2);

sub replaceInFile{
        my($file,$searchStr,$replaceStr) = @_;
        my @content = &getFileContent($file);
        
        
        foreach my $line(@content){
                print "line --> $line";
                $line = s/$searchStr/$replaceStr/g;                     
        }
        
}