use strict;
use warnings;
my %umlaute = (
                'ö' => 'oe',
                'ü' => 'ue',
                'ä' => 'ae'
              );
my $var1 = "Dorfstr";

my $var2 = "Brandstroemweg";

for ($var1,$var2) {
s/(ä|ü|ö)/$umlaute{$1}/g;
s/str(?=\b)//g;
print;
}

DorfBrandstroemweg