Please wrap code in <code>...</code> tags. See How do I post a question effectively?. Also, the code you quote comes from perlretut. It would have been helpful if you had mentioned this.

i find an error message

#! perl
use strict;
use warnings;

my $x =  "Mmm...donut, thought Homer";
   $x =~ /^(Mmm|Yech)\.\.\.(donut|peas)/;   # matches

foreach my $expr (1 .. $#-)
{
    printf "Match %s: '%s' at position (%d, %d)\n",
            $expr,
            substr( $x, $-[$expr], $+[$expr] - $-[$expr] ),  # fixes t
+he error
            $-[$expr],
            $+[$expr];
}
[download]

please also say how can we find the number of matches for any regexp.

print "Number of matches: $#-\n";
[download]

HTH,