# html
<tr><td>Username<td><td><input type="text" name="username" size="25"></td></tr>

# cgi
my $username = seewhatsthere(
  data     => param('username'),
  field    => 'Username',
);

sub seewhatsthere {
  my %hash = @_;
  html_start();
  print Dumper(%hash);
  exit(0);
}

# Dumped
$VAR1 = 'data'; $VAR2 = ''; $VAR3 = 'field'; $VAR4 = 'Username';