--- Michael Alipio <[EMAIL PROTECTED]> wrote:
> I see... so in substitutions, all patterns in the left side are those that
> have to be substituted, regardless of which is enclosed in parenthesis.
Well, with a lot of hand-waving, then yes, that's basically correct.
(There are exceptions, but those are generally for advanced features you're
unlikely to encounter right now and that would be a distraction to the
current topic).
> However in a plain regexp look ups, only those inside the parenthesis are
> being matched...
No, not correct. The regular expression is what's being matched. Period.
The capturing parentheses merely capture some of all of the regular
expression into a 'dollar digit' variable ($1, $2, and so on).
So for this:
$var =~ s/foo(bar)/$1/;
The 'foo(bar)' is what is being matched and the 'bar' is captured to the $1
variable. For this:
if ( $var =~ /foo(bar)/ ) { ... }
The 'foo(bar)' is *still* what is being matched and the 'bar' is *still* what
is being captured to the $1 variable.
The first version is when you want to alter the string you're matching. The
second version is good when you want to take action based upon a match and
possibly extract data out of the string.
Cheers,
Ovid
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