You have a couple of answers, but some documentation references may help for the future. Files that contain tab separated data are best processed using one of the modules that understand CSV such as Text::CSV or Text::xSV.

Then there is the question of what is a suitable data structure. If "unique element" pops into your head in relation to some aspect of teh data, then you should immediately think "hash". If "sort this stuff by that key" is a factor then think 'Schwartzian transform' (see replies to What is "Schwarzian Transform" (aka Schwartzian)).

and we all need a good LOL from time to time, but in Perl that's something quite different than you might expect - see perllol. Note that LoL is closely related to HoH, HoL, LoH and those are all top of the heap for a pile of other interesting Perl data structures. Master LoL and the others should just drop out of the heap as you need them.