If require isn't failing on loading the file, then I'd suspect that the sub in question has been removed from the required file, or renamed. Have you checked to see whether someone's played with that file?

The following code snip will print out all subs currently within your namespace. Run it after the require and look for the sub in question, and see if other subs from that file have loaded properly.

use warnings;
use strict;

require "file";

my @list = keys %main::;

for (@list){
    my $sub = "main::$_";
    print "$_\n" if defined &$sub;
}
[download]

ps. If you haven't already, I'd *highly* recommend that you get all of your files checked into a version control system, so you can track this kind of thing.