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  • C-style escaped (backwhacked) character representing backspace. On most terminals this just moves the cursor one cell to the left (and even then it is unspecified what happens when the cursor is on the first cell of the line). On a hardcopy terminal (lacking TypEx), the next character will overprint. So "a\b_b\b_c\b_" or "abc\b\b\b___" might be printed as abc, and "a\bab\bbc\bc" or "abc\b\b\babc" might be printed as abc.
  • In Perl regexps, a zero-width "assertion" matching at the boundary between a word character (see \w) and a non-word character (see \W, which unfortunately shares the same E2 node). For instance, to find all occurances of the word "the", use "m/\bthe\b/". "m/the/" doesn't work, because it also finds "mother"; "m/\Wthe\W/" also doesn't work, because it fails to find "the" when situated at the very beginning or end of the string. (It is possible to write an appropriate regexp which does this correctly, but it is much longer-winded than would be sensible to write...)

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