use a Config::* module that allows writting:

  #!/usr/bin/perl

  use warnings;
  use strict;

  use Config::Properties::Simple;

  my $cfg=Config::Properties::Simple->new(scope=>'user', optional=>1);
  my $count=$cfg->getProperty(counter => 0);

  print "counter: $count\n";

  $cfg->setProperty(counter => ++$count);
  $cfg->save;
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You should also use some lock to ensure that only one process reads and increments the counter.