When troff reads a macro or string definition, it is in ``copy mode''. The following sequences are hot (and must be suppressed by adding a backslash if they're supposed to be copied unscathed, which is usually what you want):
- \n
- inline number register
- \*
- inline string registers
- \$
- inline macro arguments
- \nl
- escaped newlines are stripped
- \"
- comments are stripped
- \t
- becomes tab
- \a
- becomes SOH
- \\
- becomes \ (backslash)
- \.
- becomes . (dot)