Unfortunately, also totally wrong as it will consume an A, C, G or T adjacent to the Ns. Rather than split do a global match for one or more of A, C, G or T.

$ perl -E '
$seq = q{NNACGTNNNACGTNACGTNN};
say for split m{[ACGT]N+[ACGT]}, $seq;
say q{-} x 10;
say for $seq =~ m{[ACGT]+}g;'
NNACG
CG
CGTNN
----------
ACGT
ACGT
ACGT
$

[download]

I hope this is helpful.

Update: Corrected wording, s/more than one of/one or more of/

Cheers,

JohnGG

In reply to Re^3: Splitting only on internal pattern, not at start or end of string by johngg
in thread Splitting only on internal pattern, not at start or end of string by BiologySwede

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