for ( $sysDescr ) {

##</code><code>##

foreach $hostName (@serverList) {
    print STDERR "--- Server: $hostName\n";

    # snmpwalk as filehandle
    #----------------------------------
    $FH_SNMPWALK = new FileHandle "$SNMPWALK $hostName $oidNbrSysDescr
+ 2>&1|";
    die "$0: $! in Zeile: ", __LINE__ unless defined $FH_SNMPWALK;

    # execute snmpwalk 
    #----------------------------------
    while( $sysDescr = <$FH_SNMPWALK> ) {
      chomp $sysDescr;
      print STDERR "   Desc: $sysDescr\n";

      for ( $sysDescr ) {
           print STDERR "   in_for: $_\n";

##</code><code>##

         if (s/$prefixSysDescr/$hostName$TAB/ or s/snmpwalk:\s*/$hostName$TAB/) {
            $OutputLine = $_;
            last;
         }; # substitute some prefixes (this one works)

##</code><code>##

         if (s/($prefixSysDescr|snmpwalk:\s*)/$hostName$TAB/) {
            $OutputLine = $_;
            last;
         }; # substitute some prefixes