my $code = "xyzzy";
    for ( my $i = 0 ; $i < $l ; $i++ ) {

        $code =~ s/xyzzy/
        foreach my \$nucl (\@nucleotides) {
            substr( \$cand_motif, $i, 1 ) = \$nucl;
            xyzzy
        }
/;

    }
        $code =~ s/xyzzy/
            push \@enumerated_motifs, \$cand_motif;
            #print "\$cand_motif\\n";
/;

    eval $code;