I think you will still have to poll something in a loop though...
How about checking the mtime attribute to stat(filename)?

# could do stat()[9] and not use File::stat
use File::stat qw(:FIELDS);

$cfgfile = '/my/config/variables.file';

stat($cfgfile) or die "No $cfgfile: $!";
my $last_mtime = $st_mtime;
parse_config($cfgfile);
#time passes
#enter loop of things to do and events to check
stat($cfgfile) or die "No $cfgfile: $!";
if ($last_mtime != $st_mtime) {
  $last_mtime = $st_mtime;
  parse_config($cfgfile);
}
# sleep(N) unless something else to do
[download]

Dingus

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