Question

I’ve got some data that I’m parsing in Perl, and will be adding more and more differently formatted data in the near future. What I would like to do is write an easy-to-use function, that I could pass a string and a regex to, and it would return anything in parentheses. It would work something like this (pseudocode):

sub parse {
  $data = shift;
  $regex = shift;

  $data =~ eval ("m/$regex/")
  foreach $x ($1...$n)
  {
    push (@ra, $x); 
  }
  return \@ra;
}

Then, I could call it like this:

@subs = parse ($data, '^"([0-9]+)",([^:]*):(\W+):([A-Z]{3}[0-9]{5}),ID=([0-9]+)');

As you can see, there’s a couple of issues with this code. I don’t know if the eval would work, the ‘foreach’ definitely wouldn’t work, and without knowing how many parentheses there are, I don’t know how many times to loop.

This is too complicated for split, so if there’s another function or possibility that I’m overlooking, let me know.

Thanks for your help!

Answer 1

In list context, a regular expression will return a list of all the parenthesized matches.

So all you have to do is:

my @matches = $string =~ /regex (with) (parens)/;

And assuming that it matched, @matches will be an array of the two capturing groups.

So using your regex:

my @subs = $data =~ /^"([0-9]+)",([^:]*):(\W+):([A-Z]{3}[0-9]{5}),ID=([0-9]+)/;

Also, when you have long regexes, Perl has the x modifier, which goes after the closing regex delimiter. The x modifier allows you to put white-space and newlines inside the regex for increased readability.

If you are worried about the capturing groups that might be zero length, you can pass the matches through @subs = grep {length} @subs to filter them out.