I remember, some time ago, looking under the hood of Algorithm::Combinatorics, to find it somewhat inefficient. The ntheory equivalents, if they exist, are faster:

use ntheory 'forcomb';
sub Eily_LanX_vr {
    my ( $length, $ones ) = @_;

    my ( $str, $s, @r );
    $str = '0' x $length;
    forcomb {
        $s = $str;
        substr $s, $_, 1, '1' for @_;
        push @r, $s;
    } $length, $ones;
    
    return \@r
}

cmpthese(-3, {
    Eily_LanX_vr => sub { Eily_LanX_vr(25, 5) },
    Eily_LanX    => sub { Eily_LanX(25, 5) },
});

__END__

               Rate    Eily_LanX Eily_LanX_vr
Eily_LanX    11.9/s           --         -59%
Eily_LanX_vr 29.0/s         143%           --

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In reply to Re^3: Generate all unique combinations of 1 and 0 using specified length of "0"-string and count of 1's by vr
in thread Generate all unique combinations of 1 and 0 using specified length of "0"-string and count of 1's by Lana

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