Often, when coding scripts, I encounter situations where I need to test to see if a variable matches an item that's stored in a list of values.

One approach I've used is to maintain an array that is reviewed for the match using a "foreach" type iteration.

Another approach is to maintain a hash, and test for the presence of a hash value that matches.

It seems that using the second approach is more efficient from both an operating system standpoint, and a coding standpoint: 
foreach (@whatever) {
    if (/^does this match$/) {
        do something;
    }
}

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Vs. 
if (/$hash{$whatever}/) {
    do something;
}

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Assuming I'm thinking correctly so far, my next question has to do with creating the hash value. Is there anything "wrong" with populating a hash with keys and values that are the same? For example: 
%SampleHash (
    'whatever' => 'whatever',
    'whoever' => 'whoever',
)

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It feels like there's something wrong (or maybe more accurately, inefficient) using a hash this way, but I'm not smart enough to know if that is in fact true.

When I use hashes as described above, things seem to work OK ... I'm just wondering/hoping that some of the brainier participants here might be able to point out errors in my thinking, and/or more appropriate ways of how to handle this type of situation.

In reply to Creating lists using a hash with the same key/values by Hagbone

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