how do you use the index function on this example?

[Anonymous Monk]

Dear Monks,
I need to use the index function and I found this example:

 #!/usr/bin/perl
  use strict;
  use warnings;

  my $string = 'perlmeme.org';
  my $char = 'e';
  my $offset = 0;

  my $result = index($string, $char, $offset);

  while ($result != -1) {

    print "Found $char at $result\n";

    $offset = $result + 1;
    $result = index($string, $char, $offset);

  }

This is very straightforward, BUT, how could one find all occurences of a string that is now known exactly beforehand?
Consider the string:

$string = 'IIIIMMMMMMMOOOOOOOOOOMMMMMMMMMMMMMMMIIIIIIMMMMOOOO';

and say you would like to find all occurences (starting positions and lengths) of the M's substrings.
How do I need to proceed?

[Anonymous Monk]

Ah, never mind, I found this solution:


while($string=~/(M+)/g)
{
    ($start, $end) = ($-[0], $+[0]);
    print $start."\t".$end."\n";
}


Thanks

[AnomalousMonk]

And you don't even need the capturing parentheses:

c:\@Work\Perl>perl -wMstrict -le
"my $string = 'IIIIMMMMMMMOOOOOOOOOOMMMMMMMMMMMMMMMIIIIIIMMMMOOOO';
 ;;
 while ($string =~ /M+/g) {
   my ($start, $end) = ($-[0], $+[0]);
   print qq{start $start, end $end};
   }
"
start 4, end 11
start 21, end 36
start 42, end 46

Note that  @+ holds the positions of the first character after matched sub-strings!