[Groff] Undocumended .if "feature"

[carsten . kunze]

Hello,

in a manual page I found the commands

.ie '\*[.T]'utf8'
.  ds Un \[cu]
.el
.  ds Un U
.

The .ie and .el lines don't end with a backslash.  Nethertheless this works 
with groff.  Is this documented?  If not this is a misleading "feature" since 
it doesn't tell the author that this code has a syntax error.  IMHO the correct 
behaviour would be to ignore the .ie and .el line (because of the wrong syntax) 
and to apply both .ds commands.

--Carsten