The pattern match operator returns a list - you can say

@list = $string =~ /(regex1)(regex2)/;
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you can also say

( $match1, $match2 ) = $string =~ /(regex1)(regex2)/;
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which is why you have the parentheses. You just have one item in the list in your example.

If you omit the parentheses you just get the number of matches, ie the list is forced to scalar context. In your example you get 0 or 1.

This is useful because you can say

if ( $string =~ /(regex1)/ ){
  $found = $1;
}
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As for question 2, I can't see how it does. There is a typo in your line:

if(@ARGV && $ARGV[0] =~ /'^-') {
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If as you say this is to check that it starts with a '-', then I would guess that you mean:

if(@ARGV && $ARGV[0] =~ m'^-') {
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Then the if block would only be entered if $ARGV[0] starts with "-". In the block, $count only gets a value if $ARGV[0] starts with one or more digits. Which it can't because it starts with a "-"!

-- iakobski