Firstly read perldsc then you can try this approach:

while reading the file, chomp the line, split the line using '| ' havi
+ng back col1 and col2 then push into the hash key col1 the value of c
+ol2. Hint: being values of the hash all arrayrefs you need some deref
+encing like in @{ $hash{ $col1 } } doing the push.
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