$ alias tperl="time perl -w -Mthreads -Mthreads::shared"

# No data to copy:
 $ tperl -e'threads->create(sub{})->join() for 1..100'
 $ tperl -e'threads->create(sub{})->join() for 1..100'
CPU 0.680 secs (CPU 0.256 secs)

# Load the data late so also no data is copied:
 $ tperl -e'BEGIN{threads->create(sub{})->join() for 1..100}my @x=(1..35_000)'
CPU 0.728 secs (CPU 0.268 secs)
 $ tperl -e'BEGIN{threads->create(sub{})->join() for 1..100}my @x;share(@x);@x=(1..35_000)'
CPU 0.840 secs (CPU 0.364 secs)

# Overhead of copying, whether shared() or not:
 $ tperl -e'my @x;share(@x);@x=(1..35_000);threads->create(sub{})->join() for 1..100'
CPU 2.272 secs (CPU 1.316 secs)
 $ tperl -e'my @x=(1..35_000);threads->create(sub{})->join() for 1..100'
CPU 3.304 secs (CPU 3.384 secs)

##</code><code>##

 $ tperl -e'my @x=(1..35_000);threads->create(sub{for(@x){my$y=$_}})->join() for 1..100'
CPU 4.324 secs
 $ tperl -e'my @x;share(@x);@x=(1..35_000);threads->create(sub{for(@x){my$y=$_}})->join() for 1..100'
CPU 17.281 secs

##</code><code>##

 $ tperl -e'fork && exit for 1..100'
CPU 0.044 secs (CPU 0.020 secs)
 $ tperl -e'my @x=(1..35_000);share(@x);fork && exit for 1..100'
CPU 0.072 secs (CPU 0.072 secs)
 $ tperl -e'my @x=(1..35_000);for(1..100){if(fork){for(@x){my$y=$_};exit}}'
CPU 0.084 secs

##</code><code>##

# Try to load the data late but mostly fail:
 $ tperl -e'threads->create(sub{})->join() for 1..100;my @x=(1..35_000)'
CPU 2.048 secs (CPU 1.204 secs)

# Note how easy it is to do it wrong and not share data but get the overhead:
 $ tperl -e'my @x=(1..35_000);share(@x);print "($x[0])\n";threads->create(sub{})->join() for 1..100'
Use of uninitialized value in concatenation (.) or string at -e line 1.
()
CPU 3.380 secs (CPU 2.128 secs)