use strict;
my $persistentVar = $defaultvalue;
if( -e $persistentStateFile )
{
  open FH, $persistentStateFile 
    or die "Failed to open '$persistentStateFile': $!";
  local $/, $@;
  my $ps = <FH>;
  eval $ps;
  die $@ if $@;
}

END{
  open FH, "> $persistentStateFile"
    or warn "Failed to open '$persistentStateFile': $!" and exit(1);
  print FH Data::Dumper->Dump( [$refToPersistentVar], ['nameofpersistentvar'] ) 
    or warn "Failed to print persistent data, $!" and exit(1);
  close FH 
    or warn "Failed to close $persistentStateFile, $!" and exit(1);
}

##</code><code>##

END {
    open FH, "< $0" or warn "Failed to preserve state... couldn't open '$0', $!" and exit(1);
    local $/;
    $_ = <FH>;
    s/my \$var=$oldvalue/my \$var=$var/m;
    open FH, "> $0" or warn "Failed to preserve state... couldn't write to '$0', $!" and exit(1);
    print FH $_;
    close $file;
}