Any named parameter not explicitly supported by CGI.pm's methods will be passed along as-is into the tag:

chh@scallop chh> perl '-MCGI qw(:standard)' -le 'print td({-BOB => "fo
+o", -CAT => "bar"}, "lala")'
<TD BOB="foo" CAT="bar">lala</TD>
chh@scallop chh>
[download]

And you can always write the HTML yourself. I don't particularly like CGI.pm's HTML-generating methods.