When I looked at your string, I realized that it is actually a kind of key-value pair. My suggestion is to save the result returned from m// into a hash.

Make some small modification to the following code I gave, you can easily make it work for you:

use strict;

my $string = "DEFINITION  BIO5 gene complete cds EC=1.7.7.1.
ACCESSION   D17396
VERSION     D17396.1  GI:498167
KEYWORDS    protein; insulin-like protein;";

my %KVpairs = ($string =~ /(\w+)\s+(.*)/mg);#save the result right int
+o a hash
foreach (keys %KVpairs) {
   print "[$_] = $KVpairs{$_}\n";
}
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