Hi kcott,
OK, that got a bit of a chuckle as /3$/ was really intended as a non-solution to highlight the lack of information provided in the question...

Sorry, I misunderstood your write up. But I kind of see a solution in it, that was why I mentioned it.
Thinking if what the OP has is a file that contain say

abcd_efgh-1.2.3
abcd_efgh-1.2.3-hjik-3.4.5.tar.gz
[download]

then simply doing this:

while (<DATA>){
   print $_ if /3$/; 
}
[download]

prints abcd_efgh-1.2.3, and thanks to if /3$/; of course using ONLY these OP strings. It could be a different thing if there are other strings ending with "3".
All that been said on the assumption that, that was what was intended by the OP.