Below is a better reduction of the original code that gave me a problem and started me down this road.

I am not quite sure what you mean by I believe that your for loop should loop over (1..$#-)? As opposed to 1..$#+?

perlvar says:

You can use $#- to determine how many subgroups were in the last successful match

and You can use $#+ to determine how many subgroups were in the last successful match

Doesn't this mean they should be the same?

Update:I just found this in Japhy's book...

The last index of @-, $#-, is the number of the last matching back-reference (and so can be used to find out which $DIGIT variable $+ corresponds to), whereas the last index of @+, $#+, is the number of back-references, defined or not

Which explains things somewhat. And there was I just getting comfortable with the $#array idiom:(

End update

With regard to ${1} eq $1....see below, using $1 in the first print inside the for loop gives "abc". Using ${$_} (where $_ = 1) results in the error?

I'd assume this was a throw-over from pre-strict Perl days except that (from what I read) @- & @+ didn't arrive until 5.6.

As for what I was trying to acheive.... I am only slightly embarassed to admit that I thought that the @- & @+ arrays would give me the start/stop indexs for each captured match when used with the //g option. I now see that this was wrong, but that is why I am playing with regexs...I'm attempting to understand what they can do (and how). It saddens and confuses me slightly that someone actually bothered to downvote my original question. I always thought that the only bad question was the one you didn't ask. C'est la vie.

#! perl -w
use strict;

my $haystack = "abcdefghijklmnopqrstuvwxyz";
my @needles = qw(abc cde fgh ghi ijk pqr rst xyz);

my $regex = '(' . join('|', @needles ) . ')';
print "Pre-compilation:", $regex,$/;

$regex = qr/$regex/s;
print "Post-compilation:", $regex, $/;

$haystack =~ /$regex/g;

if ($#-) {
    print "$#+ matches found", $/;
    for (1..$#+) {
        print "\$_ is $_, & \$1 is $1", $/;
        print  "$haystack contains ${$_} at $-[$_]", $/;
    }
}

__END__
C:\test>test
Pre-compilation:(abc|cde|fgh|ghi|ijk|pqr|rst|xyz)
Post-compilation:(?s-xim:(abc|cde|fgh|ghi|ijk|pqr|rst|xyz))
1 matches found
$_ is 1, & $1 is abc
Can't use string ("1") as a SCALAR ref while "strict refs" in use at C
+:\test\test.pl
line 19.

C:\test>
[download]

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