use strict;

my @values = ("B4/370", "", "B4/349", "foo/bar/foo");
foreach my $curvalue (@values) {
    print "Bau/Raum: '$curvalue'\t";
    if ($curvalue =~ m{^\s*[^/]+\s*/\s*([^/]+)\s*$}) {
        $curvalue = $1;
        print "getroffen";
    }
    print "\n";
}