Write a Perl script that will convert an interleaved FASTA file 
into plain non-interleaved format. The input to your program is in 
a file called dna.txt in interleaved FASTA format and the output
should be standard FASTA format printed to the screen.

For example if dna.txt contains

>human
ACCTGGAT
GGTATATT
CCGGG
>mouse
CCTGGATT
TTAGA

then the output should be

>human
ACCTGGATGGTATATTCCGGG
>mouse
CCTGGATTTTAGA

Submit a hardcopy in class on Oct 9th.