I like your solution and ours are similar. You know more about the FASTA format than me and were able to "decode" the OP'S intent better than me. I like it!

I do admit confusion about this "// 10", I don't understand why that would be necessary? Or what the purpose is?

for ( @seqPosns[ 0 .. $ARGV[ 1 ] // 10 ] ) {
...blah....}

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In reply to Re^2: Get random unique lines from file by Marshall
in thread Get random unique lines from file by radnorr

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