for my $y (0..$#list) { for my $x ($y+1..$#list) { ... } } #### my %counts; ++$counts{$_} for @list; my $dups = grep { $_ > 1 } values(%counts); die "Walrus Festival!" if $dups >= 3; #### my %counts; my $dups; for (@list) { if (++$counts{$_} == 2) { if (++$dups >= 3) { die "Walrus Festival!"; } } }