A little bit off-topic, but your setting of $string is rather laboriuos. Wouldn't it be much easier to use a HERE document, like so:

my $string=<<EOSTRING;
CG2B_MARGL
MLNGENVDSRIMGKVATRASSKGVKSTLGTRGALENISNVARNNLQAGAK
...
TAKFQAVRKKYSSAKFMNVSTISALTSSTVMDLADQMC
EOSTRING
[download]

?