The Difference Between + and *
You know what * means, namely match 0 or
more. If you want to match 1 or more, then use + .
The difference is important.
$_='The number is 2200 and the day is Monday'; ($star)=/([0-9]*)/; ($plus)=/([0-9]+)/; print "Star is '$star' and Plus is '$plus'\n";
You'll note that $star has no value. The match was
successful though. It managed to match 0 or more characters from 0 to 9 at the
very start of the regex.
The second regex with $plus worked a little better, because we are
matching one or more characters from 0 to 9. Therefore, unless one 0 to 9 is found the
match will fail. Once a 0-9 is found, the match continues as long as the next character is
0-9, then it stops.
Now we know this, there is another way to remove an email address from within angle brackets:
$_='My email address is <robert@netcat.co.uk> !.'; /<([^>]+)/i; print "Found it ! $1\n";
This regex matches <. Then the capturing parens
start. They have no effect on this regex other than to capture the match.
After that, there is a character class, containing one character. As ^
is the first character is the class, it negates the class. That's why
we are using a character class with only one character in it, because it can
be negated.
So far we have matched < and anything that is not >.
The + ensures we match as many characters that are not <'s as
we can. This has the same effect as .*? but is more efficient. It may also
suit your purposes, as .*? relies on you knowing what you want to match up
to, whereas [^>]+ simply contines matching until it finds something that
fails its criteria. Just make sure you understand the difference because it is a crucial
part of regexery.
