If files that you're dealing with are small; i.e., config files, etc., it's probably easier to slurp them into memory, perform modifications, truncate the file, and then write data back -- no temp files needed.

With larger files and variable-length records, it's easier to work with temp files. If you attempt to update a variable-length record file without having a temp file, the code will get very ugly in no time. Sometimes, however, you just have to bite the bullet and do it; i.e., when you deal with huge files and you can't spare space for a temp file of the same size.

If you're working with large fixed-length record files, it is almost always better and more elegant, in my opinion, to work with the original file without creating temp files.

Here's how I would approach this (not tested)

use strict;
use Fcntl ':flock';

my $iniFile = 'config.ini';
if (open my $ini, "+<$iniFile"){
  if (flock $ini, LOCK_EX){
    my @data = <$ini>;
    # Work with @data -- delete lines, update lines, etc.
    if (truncate($ini, 0) and seek($ini, 0, 0)){
      print "Can't write to $iniFile : $!\n"
                        unless print $ini @data;
    }else{
      print "Can't truncate/seek : $!\n";
    }
  }else{
    print "Can't lock : $!\n";
  }
  close $ini;
}else{
  print "Can't open $iniFile : $!\n";
}
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--perlplexer