I can only guess that the grep is matching more than one line for some of the elements in @isos20

Even assuming it did, you would still only print $line only once, since the grep is used only as a conditional for deciding whether to print or not. Your error, if any, must be somewhere else. But I can't say where, not having seen your input.

In reply to Re: grep of readline matching more lines than elements in array by Laurent_R
in thread grep of readline matching more lines than elements in array by bdorsey

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