Unfortunally, if the array is large, and there's a significant number of elements "\n" in the array, the repeated splicing can be slow. splice() is an O(n) operation (with n the length of the array), and that's a tight worst case bound (splice may require shifting half the array). If you have a large array, and cannot afford to copy, you can still remove the offending elements in situ: 
my $j = 0;
for (my $i = 0; $i < @molecules; $i ++) {
    $molecules[$j++] = $molecules[$i] unless $molecules[$i] eq "\n";
}
splice @molecules, $j;

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In reply to Re^3: Deleting specific array elements by JavaFan
in thread Deleting specific array elements by joec_

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