Sorry but your specifications are still not clear to me ... can you give a small example input and an example of the desired output.

Hi Arun,

The .RES file has many lines like: /cadappl/armrvds/2.2b616/RVCT/Programs/2.2/616/linux-pentium/tcc --cpu=ARM9E --debug --no_debug_macros --split_sections --fpu=SoftVFP -O1 --apcs /interwork -c -I../incl -I/vobs/package291/nxp49xx/modules/bbl49xx/incl -I/vobs/package275/audiocodec/modules/codeci/incl -I/vobs/package291/nxp49xx/modules/drv49xx/incl -I/vobs/package162/psenv/modules/errhdl/incl -I/vobs/package275/audiomng/modules/gaudio/incl -I/vobs/package275/audiomng/modules/gaudioi/incl -I/vobs/package155/psaudio/modules/hau/incl -I/vobs/package229/hardwl/modules/hwlaud/incl -I/vobs/package229/hardwl/modules/hwlvf/incl -I/vobs/package161/psstartup/modules/init/incl -I/vobs/package165/pskid/modules/kidglobal/incl -I/vobs/package202/pslayerone/modules/l1a/incl -I/vobs/package202/pslayerone/modules/l1s/incl -I/vobs/package141/psl23common/modules/l23guf/incl -I/vobs/package141/psl23common/modules/l23libint/incl -I/vobs/package164/psmaster/modules/master/incl -I/vobs/package163/psdef/modules/pcc/incl -I/vobs/package158/psrtke/modules/rtke/incl -I/vobs/package291/nxp49xx/modules/sys49xx/incl -I/vobs/package157/pstrace/modules/trace/incl --bss_threshold=0 --diag_suppress=1296 --diag_suppress=550 --gnu --littleend --split_sections -DA5_3_FTR....</para> <para>Now the script should process/match any ONE line (so I used --gnu, which exists in that line) and then look for -DA5_3_FTR words.

The output file (a text file) should typically look like -DARM_ITCM_ACTIVATION_HDW -DATCMD_M2M_DETACH_SWITCHOFF_SFI -DATCMD_M2M_FULL_SW_VERSION_FTR -DATCMD_M2M_PSADC -DATP_ATA_VOICE_FTR -DATP_NO_AUTOBAUDING_FTR -DATP_PPP_OVER_GPRS_FTR

...hopefully this does what you need

use strict;
use warnings;

open(OUT, '>', "out.txt");

open(FH, "test.res") or die "$!";
while(<FH>){
  chomp;
  if($_ =~ m/--gnu.+-D/){
    my @words = split(/\s+/, $_);
    foreach my $word(@words){
      if($word =~ m/^-D/){
        print OUT "$word\t";
      }
    }
    last;
  }
}
close(FH);
close(OUT);
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