This particular instance calls for arrays, like the others have said. However, for reference, you can do what you were trying to do like this:

${ 'radio_' . $ucount } = param( "radio_$ucount" );
${ "textarea$ucount" } = param( 'textarea' . $ucount );
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Note that

• Variables won't be interpolated into a string that uses single-quotes.

  print "something$ucount"; # prints 'something1'
  print 'something$ucount'; # prints 'something$ucount'
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• You can use the concatenation operator '.' (spot) to create single strings, which is often useful for clarity.

  $x = "something$ucountElse"; 
  # probably tries to interpolate a variable called 
  # $ucountElse, ambiguous
  $x = "something" . $ucount . "Else"; # Unambiguous
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• You can rewrite $name to ${'name'}, and you can interpolate this syntax too:

  $x = "something${ucount}Else";
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