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If you've got a list of things in Perl, and you want them in random order, don't try to make up a way to do it yourself. Use the shuffle function in the List::Util module. Say you want a list of files from a directory:

use List::Util;
my @files = glob( '*' );
@files = grep { -f } @files;
@files = shuffle @files;

Of course you can combine that into one expression:

use List::Util;
my @files = shuffle grep { -f } glob( '*' );

Or from the command line:

perl -MList::Util=shuffle -le'print for shuffle grep {-f} glob("*")'

Don't worry that List::Util is a module, because it's a core module that's been included with Perl since 5.7.3

$ corelist List::Util

List::Util was first released with perl 5.007003

The shuffle function is extremely simple, and how here's a little article that explains why it works.