use List::Util qw(min);
$hash{$set}{min} = min @{$hash{$set}{data}};

##</code><code>##

for (@{$hash{$set}{data}}) {
    $hash{$set}{min} = $hash{$set}{min} < $_
        ? $hash{$set}{min}
        : $_;
}

##</code><code>##

my $min := $hash{$set}{min};
for(@{%hash{$set}{data}}) { $min = $min < $_ ? $min : $_ }