use Carp qw(croak);
  
  sub htmlprint {
    my %arg = @_;
    exists $arg{file}   or croak "Expected file";
    exists $arg{text}   or croak "Expected text";
    exists $arg{colour} or croak "Expected colour";
    
    $arg{file}->printf(
      '<span style="color:%s">%s</span>',
      $arg{colour},
      $arg{text},
    );
  }