Unless you're running under DOS or C/PM, (is that even possible these days with Perl?), pipes do not touch the filesystem. They are buffered through kernel memory space.

There is the vague possibility that if your system went into swapping, and then crashed, that some small parts of the file (probably 4k), might turn up in a scan of the systems swap file somewhere.

If you use less, which allows the user to back up through the file, (as opposed to more which on my system doesn't), then there is the possibility that the system could be forced into swapping and then crashed, and the whole file picked out from the system swap file. Though it would probably be in 4k chunks mixed up amongst loads of other stuff.