I'm afraid I can't be of service. To make things worse, I have one nit to pick ;-) :

if ( -f $file && $timestamp != (stat($file))[9]

I would have written that as:

if ( -f $file && $timestamp != (stat _)[9]

According to stat:

If stat is passed the special filehandle consisting of an underline, no stat is done, but the current contents of the stat structure from the last stat or filetest are returned.

Saves one stat() to the OS.

Liz