That'd be euro_calc, then ;) (perlstyle).
Update (200201021252+0100) I like freestyle even better: $eurocalc->freestyle() :)

BTW, I'd probably have used (from, to, amount) or auto-detect the order.

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
[download]