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Benchmark: timing 100000 iterations of join, loop, quote...
join: 3 wallclock secs ( 2.30 usr + 0.00 sys = 2.30 CPU) @ 43402.78/s (n=100000)
loop: 17 wallclock secs (16.03 usr + 0.00 sys = 16.03 CPU) @ 6237.52/s (n=100000)
quote: 5 wallclock secs ( 3.79 usr + 0.00 sys = 3.79 CPU) @ 26420.08/s (n=100000)
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my @a1 = ( "3 5 7", "9 11 13" );
my @a2 = qw( 3 5 7 9 11 13 );