perl -E"
$t=time; 
++$h{ rand(10000) } while time()==$t; 
my $n=0; 
$_ > 1 and $n+=$_ for values %h; 
say $n, ' duplicates in 1 second';
"
13793 duplicates in 1 second

perl -E"$t=time; ++$h{ rand(10000) } while time()==$t; my $n=0; $_ > 1 and $n+=$_ for values %h; say $n, ' duplicates in 1 second';"
400896 duplicates in 1 second

>perl -E"$t=time; ++$h{ rand(10000) } while time()==$t; my $n=0; $_ > 1 and $n+=$_ for values %h; say $n, ' duplicates in 1 second';"
504998 duplicates in 1 second