Returning the Match
Now things get interesting. What if we want pull something out of a string ? So far all we have done is test for truth, that is say yea or nay if a string matches, but not return what we found. Run this:
$_='My email address is <Robert@NetCat.co.uk>.'; /(<robert\@netcat.co.uk>)/i; print "Found it ! $1\n";
Firstly, note the single quotes when $_
is assigned. If there were double quotes, we'd need \@ instead of @ .
Remember, double quotes "" allow variable interpolation, so Perl looks for an
array called @NetCat which does not exist.
Secondly, look at the parens around the entire regex. If you use parens, a side effect
is that the first match is put into a variable called $1 .
We'll get to the main effect later. The second match goes into $2
and so on. Also note that the \@ has
been escaped, so perl doesn't think it is an array. Remember \
either escapes a special character, or gives a special meaning. Think of it
as Superman's telephone box. Imagine Clark Kent walking around with his magic partner Back
Slash.
Notice how we specify in the regex case-insensitivity with /i
and the regex returns the case-sensitive string - that is, exactly
what it found.
Try the regex without parens. Then try this one:
/<(robert)\@netcat.co.uk>/i;
You can put the parens anywhere. More or less. Now, run this :
$_='My email address is <Robert@NetCat.co.uk>.'; /<(robert)\@(netcat.co.uk)>/i; print "Found it ! $1 at $2\n";
See, you can have more than one ! Look at the above regex. Looks easy now, don't you think ? What about five minutes ago ? It would have looked like a typing mistake ! Well, there are some hairier regex to come, but you'll have a good barber.
