Simple, assign the random index to a variable and splice using that variable: 
for (1..$a) {
        my $foo = rand @thumbs;
        my $randomelement = $thumbs[$foo];
        my $url = "picture_directory/$randomelement";

        print qq(<img src="$url">$url<br>);
        splice(@thumbs, $foo, 1);
}

[download]

Update: hooray for redundancy!

[ ar0n ]

In reply to (ar0n) Re: remove a random variable from an array by ar0n
in thread remove a random variable from an array by Anonymous Monk

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