It's quite common when outputting tabular data (be it CSV, or an HTML table) to ensure that column headers are printed once by using something along the lines of:

sub arrayref_to_csvline { ... }

my $headers;
while (my $row = $iter->())
{
  unless ($headers)
  {
    print arrayref_to_csvline($row->fields);
    $headers = 1;
  }
  print arrayref_to_csvline($row->values);
}

[download]

I recently discovered a pattern that takes advantage of the return value of print (it returns 1 on success)...

sub arrayref_to_csvline { ... }

my $headers;
while (my $row = $iter->())
{
  $headers ||= print arrayref_to_csvline($row->fields);
  print arrayref_to_csvline($row->values);
}

[download]

... just thought I'd share.

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

In reply to Printing the header row by tobyink

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