#!/usr/bin/perl
######################################################################
+###############
# findone
# usage: findone { coderef }, @array  , OPTIONAL start_index OPTIONAL 
+end_index
# Like grep but returns the first match. successive calls return succe
+ssive elements.
# Can be nested. Uses Weak references to prevent the leaking of memory
+. 
######################################################################
+###############


BEGIN {
    use warnings;
    use strict;
    use WeakRef;
    my %find_cache = ();    # Temporary Storeage.
    
    sub findone(&\@;$$) {    
    
        my $coderef = shift ;
        # Generate a key from the caller function so we can track whic
+h call it is.
        my $codekey = join(":",caller(),"$_[0]");    # Generate key 
        
        my %persistant_args = () ;

        ##############################################################
+##########
        # Clean up old keys to prevent leaking mem.  If the data does 
+not exist, 
        # then it has been freed and we don't need to keep position in
+fo.
        ##############################################################
+##########
        while(my ($k,$v) = each %find_cache){
            delete $find_cache{$k} unless defined ($v->{dataref});
        }

        unless (defined $find_cache{$codekey} ){
            %persistant_args = ('index' =>($_[1]||0), 'dataref' => $_[
+0] );
        }else{
            %persistant_args = %{$find_cache{$codekey}};
            
        }

        my $end_index = $_[2] || $#{ $_[0] };
        for  (; $persistant_args{index} <=  $end_index; $persistant_ar
+gs{index}++ ){
            $_ = $_[0]->[$persistant_args{index}];

            if (&$coderef){
                $persistant_args{index}++;
                $find_cache{$codekey} = {%persistant_args};
                weaken ($find_cache{$codekey}->{dataref});
                return wantarray ?  ($_ ,($persistant_args{index} -1 )
+ ) : $_;

            }
        
        }
        delete $find_cache{$codekey};
        return;         
     }

} 



###########################
# Silly Example           #
###########################
my @words = (qw(this Is a silly coNtrived Test)) x 5;
print "\@words is $#words\n";
while ( my ( $val ,$index ) = findone {  m/[A-Z]/   }  @words  ){
    print "_" x 40,"\n";
    print "Matched uppercase letter $val at $index \n";

    while ( my ( $otherval ,$otherindex ) = findone {  !m/[A-Z]/   }  
+@words , 10, 22  ){
        
        print "\tInner matched all lower $otherval at $otherindex\n";
    }
    sleep(1);
}
[download]

updated Changes in response to jynx
updated Changed to accept end_index as well.
updated Changed to use stringified reference in cache key.
Now you can nest them.

my @AoA = (Array of arrays);

while ( my ($val,$index) = findone { findone{ other_criteria } @{$_} } @AoA ){

}

UPDATE: Subtle Bug/Feature, see this. I have a newer version that uses Filter::Simple, but I still hope to fix this without resorting to it.
UPDATE: Rough filter simple version here.

-Lee

"To be civilized is to deny one's nature."