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$hydphb='GAFIVL'; ... $_ =~ /[$polar.$charged]([$hydphb]|[$polar]| H[$hydphb][$polar][$hydphb]W){18-24}[$polar.$charged]/;
$_ =~ /[$polar.$charged] ([$hydphb]|[$polar]){18-24} [$polar.$charged]/; $_ =~ /H[$hydphb][$polar][$hydphb]W/;