I've used something like this before, in little non-production scripts:

for my $amount ('60.00','160.00','5') {
  print "\$", pad(dollarize($amount),6), "\n";
}

sub pad {
  my $txt = shift;
  my $num = shift || 7;
  return " " x ($num - length($txt)) . $txt;
}

sub dollarize {
  my $txt = shift;
  $txt .= '.' unless $txt =~ /\./;
  $txt .= '0' unless $txt =~ /\.\d\d/;
  $txt .= '0' unless $txt =~ /\.\d\d/;
  return $txt;
}
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-Blake