problem with find -regex

[Jeffrey Richardson]

I am attempting to use the -regex option of find to find files with
various extensions.
Does the -regex option support regular expressions with parentheses? It
seems not to.

If I use ".*\.c",  I get all the .c files.
If I use ".*\.tdl, I get all the the tdl files.
If I then try to get either using ".*\.(c|tdl)", I get nothing.
In fact, if I use ".*\.(tdl)", I get nothing.
As a cluge, I try ".*\.[ctdl]+", which get to many matches because it
matches *.t, *.td, *.d, etc.

Any suggestions?
Thank you,
Jeff Richardson

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