The first question has been answered fine. I'd like to give a brief insight on the second question.

In the regex "abc" =~ /(\w)+/, one would expect $1 would be 'a', since that is the first \w matched. This is not the case -- $1 is 'c'. This is because the regex engine does this:

1: PAREN1
  2: MATCH \w OR GOTO 5
3: CLOSE1
4: GOTO 1
5: DONE
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That's a pretty dumbed-down explanation, but as you can see, $1 gets defined and redefined over and over again.

For more information, read perldebug.

$_="goto+F.print+chop;\n=yhpaj";F1:eval