sub by_priority{my$r=qr/^(?:Service|Organisation|FAQ)/;$a cmp$b|($a=~$r&-1)+($b=~$r)} 
my @foo =( "Service", "FAQ", "BrowserUK","Organization1", "FAQ2", "Organization2");
print join " ", sort by_priority @foo;

__END__
BrowserUK FAQ FAQ2 Organization1 Organization2 Service