While working on a tool for cleaning up uses clauses I stumbled upon this beast (slightly changed to protect the innocent):
{$if defined(DEBUG) or defined(DEBUG_SPECIAL)}
uses
{$ifend}
{$IFDEF DEBUG}
dialogs
{$ENDIF}
//<some comment about the following ifdef>
{$IFDEF DEBUG_SPECIAL}
mmsystem, // timeGetTime()
messages
{$ENDIF}
{$if defined(DEBUG) or defined(DEBUG_SPECIAL)}
;
{$ifend}
If you are only looking for uses clauses inside some Delphi sources and try to avoid a full featured parser, you will have a pretty hard job to detect, parse and interpret that one correctly.
So, if you are interested to make any use of such a tool, please do me a favor: Don't write your code that way! It is hard to read for humans anyway.