Off Topic RegEx Question

[David Landgren]

Roger Williams wrote:
 > I know thins is not the place but I know one of you know this one off the
 > top of your head.
 >
 > I have:
 >
 > $list = "dog 1 1 1 cat 2 1 snake 111"
 > and I want to end up with:
 > dog 1 cat 2 snake 1
 > I thought
 > $list =~ s/ \d \d/ \d/g;
 > would do the trick, but that gives me:
 > dog d 1 1 cat d snake d 1

\d in the RHS of the s/// doesn't do much (as you can see...)

Try:

$list =~ s/(\d)\d*(?: \d+)*/$1/g;

Capture a digit, maybe followed by more digits, then followed maybe by 
groups of space and digits. Replace all that by the captured digit.

Note that this will transform:

   dog 1 4 7 cat 2 1 snake 123 => dog 1 cat 2 snake 1

rather than:
   dog 1 4 7 cat 2 1 snake 123 => dog 7 cat 2 snake 3

I assume since cat 2 1 => cat 2 that you always want the first digit 
matched.

http://www.perlmonks.org/ is a good place to ask Perl questions.

David