As others have clearly pointed out, ^ matches only at the beginning of a string. Another way to make \G and ^ work in your scenario would be to lop off each match as you go (and the /c modifier is useless in this case, so it has been removed).

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

my $string = " a 1 # ";
my $i = 0;
while () {
    if ( $string =~ s/^\G\s+//g ) {
        print "whitespace\n";
    }
    elsif ( $string =~ s/^\G[0-9]+//g ) {
        print "integer\n";
    }
    elsif ( $string =~ s/^\G\w+//g ) {
        print "word\n";
    }
    else {
        print "done\n";
        last;
    }
}
[download]

I can't see much use for both being used in the same context in your case though. Found in the perlretut is use re 'debug';. Very helpful for things like this to see why parts of a regex aren't (or are) matching.

-stevieb