Possible bug in less

[QTEST]

I think I've found a bug in less.

I think it stems from the difference in the way the following two commands
are called, One with a pipe and one without, e.g.

	1) 	cat filename | less	
	2)	less filename

Both of the above commands will list the first page (assuming 'filename'
is longer than one page) and give the ":" prompt. If at this prompt
the command "!sh" is entered, command type 1) will wait for a few seconds
and then return "!done (press RETURN)". Command type 2) will correctly
spawn the shell and repond with the usual PS1 prompt.

My question is; why does the first command, i.e. the one using the pipe
NOT spawn a shell, but simply return to less?
Are the above differences a result of the pipe?
By the way my version of less was compiled on SVR2 if that helps.

			qtest  {ihnp4}whuxl!qtest