ctactaaacgcatcttctttgcgcggta GACGAGTGAGCGGCATCCAGCATTAA $ perl unwrap_fasta.pl coding.fasta unwrap.fasta $ cat unwrap.fasta > NP_414542 ATGAAACGCATTAGCACCACCATTACCACCACCATCACCATTACCACAGGTAACGGTGCGGGCTGA > NP_414617 ATGACTCACATCGTTCGCTTTATCGGTCTACTACTACTAAACGCATCTTCTTTGCGCGGTAGACGAGTGAGCGGCATCCAGCATTAA See a sample answer here . display_codon Read a fasta file that contain protein-coding sequences. Re-format the sequences to show codons (10 codons per line) in the output file. Hint: learn about the substr function