#!/usr/bin/perl
use strict;
use warnings;

local $/; # Slurp
my $content = <DATA>;

my ($header) = $content =~ /^(>.*?)$/m;
while ($content =~ /^[\w]+?([VMFWLCA]{8,})[\w]+?$/mg) {
    my $sequence = $1;
    print $header, "contains $sequence at position ", pos($content) - length($sequence), "\n";
}
__DATA__
>P30450 | Homo sapiens (Human). | NCBI_TaxID=9606; | 365 | Name=HLA-A; Synonyms=HLAA;M

MAVMAPRTLVLLLSGALALTQTWAGSHSMRYFYTSVSRPGRGEPRFIAVGYVDDT
QFVRFDSDAASQRMEPRAPWIEQEGPEYWDRNTRNVKAHSQTDRANLGTLRGYYNQSEDGS
TIQRMYGCDVGPDGRFLRGYQQDAYDGKDYIALNEDLRSWTAADMAAQITQRKW
ETAHEAEQWRAYLEGRCVEWLRRYLENGKETLQRTDAPKTHMTHHAVSDHEATL
RCWALSFYPAEITLTWQRDGEDQTQDTELVETRPAGDGTFQKWASVVVPSGQEQ
RYTCHVQHEGLPKPLTLRWEPSSQPTIPIVGIIAGLVLFGAVIAGAVVAAVMWRRKS
SDRKGGSYSQAASSDSAQGSDMSLTACKV