}
    }
    if ($cr eq '') {
	return;
    }

    # call cr(arg1,arg2,...)
    if (-e "$cr.pm") {
	no strict 'refs';		# allow symbolic references
	my $expr = $expressions[$i];
	eval "require $cr";
	$cr->import (@_[1 .. $#_]);    
	&$cr ($expr);
	use strict 'refs';
    }

}
#-------------------------------------------------------------------------------
sub display_subexpressions() {

    for ($i = 0; $i <= $#expressions; $i++) {
	my $prefix = " ";