http://www.perlmonks.org?node_id=188743

grain_of_sand has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to debug my understanding of the matching operator. When invoked with the g modifier in list context, I thought that the return value is a list of all possible matches. If capturing parentheses are used, then the list is the set of all $1, $2, etc captured.

The following bit of Perl:
#!/bin/perl -w $" = '-'; $string = "a:b c:d"; @list = ($string =~ m/(\w):(\w)/g); print "list=@list\n"; $string = "a:b:c"; @list = ($string =~ m/(\w):(\w)/g); print "list=@list\n";
prints out:
list=a-b-c-d list=a-b
I understand the first line of output, but it seems to me that the second line of output should really be:
list=a-b-b-c
This is because the (\w):(\w) can match a:b and also b:c. It appears that the regex engine finds the first match of a:b and then starts the next matching attempt after the b, in which case it cannot find the b:c match. I expected the next matching attempt to start after the a, so that the b:c match would also be found.

I have read the Camel book chapter on this & the perlop man page, but they don't really have a lot to say about this...

grain_of_sand