In addition to many of those already mentioned, I'm really interested in the family of PDL modules which looks to be very useful in some of the large data manipulations I run into from time to time. From the FAQ:

PDL stands for Perl Data Language . To say it with the words of Karl Glazebrook, initiator of the PDL project: The PDL concept is to give standard perl5 the ability to COMPACTLY store and SPEEDILY manipulate the large N-dimensional data sets which are the bread and butter of scientific computing. e.g. $a=$b+$c can add two 2048x2048 images in only a fraction of a second.

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I'd like to be able to assign to an luser