elsif($winners eq "denmark\n")
{
        print "Denmark - people at competition:\n";
        
        foreach $guest(@people)
        {
            if(length($guest->{'id'}) == 15 && $guest->{'id'} =~ /^20[0-5]|^26|^28/)
            {
                   &write(#dont know what parameters should give)
            }
        }
    }
# My function
sub write
{
    print "$guest->{'surname'} ";
    print "$guest->{'name'}";
    print ":$guest->{'id'}\n";
}

If i do it like this it works without problem
elsif($winners eq "denmark\n")
{
        print "Denmark - people at competition:\n";
        
        foreach $guest(@people)
        {
            if(length($guest->{'id'}) == 15 && $guest->{'id'} =~ /^20[0-5]|^26|^28/)
            {
                   print "$guest->{'surname'} ";
                     print "$guest->{'name'}";
                   print ":$guest->{'id'}\n";
            }
        }
    }