while(<DATA>){
   if (/2/){
      my $skip=2;
      print "skipping $skip lines\n";
      <DATA> while $skip-- >0 and not eof DATA;
      next;
   }
   if (/5/){
      print "high five\n"; next;
   }
   if (/3/){
      print "I am not here\n"; next;
   }
   print;
}

__DATA__
1
1
2
3
4
4
5