use strict;
use Data::Dumper;

my %att = (PREEXISTING => "val1", ANOTHER => "Val2");

my $Incoming = q{uno="one" Blah blah dos="two"  * More Noise* tres="three"};

while ($Incoming =~ m/\W*(\w+)="(.*?)"/g) {
	$att{uc $1} = $2;
}

print Dumper \%att;