c:\test>perl -MMath::Random::MT=rand -E"$t=time; 1 while time==$t; ++$h{ rand(10000) } while time()==$t+1; my $n=0; $_ > 1 and $n+=$_ for values %h; say $n, ' duplicates in 1 second';"
4 duplicates in 1 second

c:\test>perl -MMath::Random::MT=rand -E"$t=time; 1 while time==$t; ++$h{ rand(10000) } while time()==$t+1; my $n=0; $_ > 1 and $n+=$_ for values %h; say $n, ' duplicates in 1 second';"
4 duplicates in 1 second

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