Concurring with
davido's suggestion that we need a clearer problem statement (and probably one that seeks to deal with a single topic at a time), here's an answer to question in your node title:
C:>perl -E "my @x=qw(3 4 5); say @x; $x[2] = E; say @x;"
345
34E
Questions containing the words "doesn't work" (or their moral equivalent) will usually get a downvote from me unless accompanied by:
- code
- verbatim error and/or warning messages
- a coherent explanation of what "doesn't work actually means.