How about you just List::Util shuffle 1 to 15 and then splice the first 5:

#!/usr/bin/perl

use Data::Dumper;
use List::Util 'shuffle';

my @list = ( 1 .. 15 );
print Dumper( \@list );

my @shuffled = shuffle(@list);
print Dumper( \@shuffled );

my @five = splice( @shuffled, 0, 5 );
print Dumper( \@five );
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