At my previous employer I wrote a telecoms billing application in perl. It ran as a daemon which listened for events from a telecoms switch (like "call started", "call still in progress", "call ended") figured out whether the call was local, single tandem, dual tandem, international, which other telcos were involved, who to bill, how much to bill 'em, how much we would be billed, did descending balance billing for customers, some fraud detection and so on. It could also bill based on historical call data, and I managed to get it down to processing a month of data in 18 hours.

They also used another perl application - which also ran as a daemon - for controlling the switch. When a call came in, it would look stuff up in a routing database and pick the least-cost route for that combination of caller and recipient and the time of day. This - of course! - had to work in as near as damnit real time.

All of this was running on decidedly low-endian hardware.

My current employer makes several million a year from a very simple little perl app which provides a web services interface between one of our biggest customers and our SAP backend so they can place orders automagically.

Several of my projects for this year are going to involve using perl to talk to an SAP backend.