More to your satisfaction?

#! perl -slw
use strict;
use Math::Random::MT qw[ rand srand ];

$|++;
my @c = ( 'A'..'Z', 'a'..'z', 0..9 );

for my $run  ( 1 .. 1e6 ) {
    my %seen; keys %seen = 1e6;
    printf "\rrun: $run";
    for my $id ( 1 .. 1e5 ) {
        srand( $run * $id );
        for( 1 .. 10 ) {
            my $ID = join '', map $c[ int rand( 62 ) ], 1 .. 25;
            warn "Dup $ID at $run/$id" if exists $seen{ $ID };
            undef $seen{ $ID };
        }
    }
}

__END__
C:\test>"IDrand(62)x25.pl"
run: 54
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