.TH test 1 test test
.SH FOO

.\" There is no problem here
.IR 'foo1
.IR .foo1

\fI'foo2\fP
\fI.foo2\fP

.\" bug in a groff page:
.br
\fI.foo3\fP

.br
\fI'foo3\fP

.\" This is correct:
.br
\fI\&.foo4\fP

.br
\fI\&'foo4\fP

.\" po4a should not generate such a buggy page. It should add a \&
.br
.I .foo5

.br
.I 'foo5