grep is grepping everything. I've never had this problem with grep before.

You are using:

grep( lc $word, @short_sizes )
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grep passes through any value where the expression (first argument) is true.

Your grep expression is lc $word. If $word has any value except undef, '' or 0, then lc $word will also have a value, and therefore be true, and everything in @short_sizes will pass through.

Since if( grep( ...,... ) ) { places grep in a scalar context, the result will be the number of items passed through, which will be the same as the number of elements in @short_sizes. So, unless it is empty, the if condition will be true.

Effectively, if (grep(lc $word,@short_sizes)) {

is the same as:if( defined( $word ) && @short_sizes > 0 ) {

which almost certainly isn't what you intend.

So, what are you trying to achieve with that construct?

If you are trying to check if any of the values in @short_sizes matches the lower cased value of $word, the you would need:

if( grep( $_ eq lc $word, @short_sizes ) ) {
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But that's just my guess as to your intent.