Here's the trick:
the keys function returns an array.
When you do 
keys @import_values{"ship","weight","dwg","rev"}

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You are causing something very funky 
%import_values{"ship","weight","dwg","rev"}

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Is a syntax error. 
@import_values{"ship","weight","dwg","rev"}

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Is trying to take a hash slice, which works, but returns an array, and keys expects a hash.

As others have said, just use keys %hash.

The other (not as good, but preserves order of keys) way would be: 

foreach $value3 (@import{'ship','weight','dwg','rev'})

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See perldata, line 867 or so, for discussion of hash slices

In reply to Re: hashes by swiftone
in thread hashes by jrsmith

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