sub check_errors {
  return unless ($ERRORCHECK == 1);
  my $st = system("ask-yes-no", "There were errors. Do you want to continue?") >> 8;
  if ($st != 0) {
    # exit the program
  }
}

##</code><code>##

...do stuff...
check_errors();
...do more stuff...
check_errors();
... etc.