#! /usr/bin/perl
use strict;
use warnings;
use List::Util qw( sum );

my @values;

{
    # jeweils blockweise einlesen bis zum "end\n"
    local $/ = "end\n";
    while ( my $dataset = <DATA> ) {

        my @values = grep { m{^[\d.]+$} }
          split m{\n}, $dataset;

        next if !@values;

        my $average = sum(@values)/@values;
        print $average, "\n";
    }
}



__DATA__
start
0.23
0.32434
0.234
1.0
end
start
0.3423
1.4
end
final