my $usage = <<EOF

usage: $0 [-flags] <fasta file> <output file> (must be all 1 type.
    ie all fasta NT, all fastq, all fasta fna)

etc...

EOF

##</code><code>##

if( ( $#ARGV + 1 ) < 1 ) {
    die $usage;
}

##</code><code>##

die $usage unless @ARGV;