#Store an entry:
$speed[1][1]['weekday']= 32.61712;
#or when you load values from a CSV file (I assume all values on one line:
my $line=<csvfile>;
my @speeds= split $line;
my $link_no=1;
my $i=1;
my $day='weekday';
foreach (@speeds) {
  $speed[$link_no][$i++][$day]= $_;
}