#!perl -l

sub Iterator (&) { $_[0] }

sub igrep (&$) { 
	my ($check, $iterator) = @_;
	sub {
		local *_;
		my @data;
		my $wantarray = wantarray;
		while(@data = ($wantarray ? $iterator->() : scalar $iterator->())) {
			*_ = \ $data[0];
			return $wantarray ? @data : $data[0] if $check->(@data);
		}
		return undef;
	}
}