Tgrep2 operators
A < B       A is the parent of (immediately dominates) B.
A > B       A is the child of B.
A <N B      B is the Nth child of A (the first child is <1).
A >N B      A is the Nth child of B (the first child is >1).
A <, B      Synonymous with A <1 B.
A >, B      Synonymous with A >1 B.
A <-N B     B is the Nth-to-last child of A (the last child is <-1).
A >-N B     A is the Nth-to-last child of B (the last child is >-1).
A <- B      B is the last child of A (synonymous with A <-1 B).
A >- B      A is the last child of B (synonymous with A >-1 B).
A <` B      B is the last child of A (also synonymous with A <-1 B).
A >` B      A is the last child of B (also synonymous with A >-1 B).
A <: B      B is the only child of A.
A >: B      A is the only child of B.
A << B      A dominates B (A is an ancestor of B).
A >> B      A is dominated by B (A is a descendant of B).
A <<, B     B is a left-most descendant of A.
A >>, B     A is a left-most descendant of B.
A <<` B     B is a right-most descendant of A.
A >>` B     A is a right-most descendant of B.
A <<: B     There is a single path of descent from A and B is on it.
A >>: B     There is a single path of descent from B and A is on it.
A . B       A immediately precedes B.
A , B       A immediately follows B.
A .. B      A precedes B.
A ,, B      A follows B.
A $ B       A is a sister of B (and A != B).
A $. B      A is a sister of and immediately precedes B.
A $, B      A is a sister of and immediately follows B.
A $.. B     A is a sister of and precedes B.
A $,, B     A is a sister of and follows B.
A = B       A is also matched by B.

Regular expression operators
"."      Matches any character except a newline.
"^"      Matches the start of the string.
"$"      Matches the end of the string or just before the newline at
         the end of the string.
"*"      Matches 0 or more (greedy) repetitions of the preceding RE.
         Greedy means that it will match as many repetitions as possible.
"+"      Matches 1 or more (greedy) repetitions of the preceding RE.
"?"      Matches 0 or 1 (greedy) of the preceding RE.
*?,+?,?? Non-greedy versions of the previous three special characters.
{m,n}    Matches from m to n repetitions of the preceding RE.
{m,n}?   Non-greedy version of the above.
"\\"     Either escapes special characters or signals a special sequence.
[]       Indicates a set of characters.
         A "^" as the first character indicates a complementing set.
"|"      A|B, creates an RE that will match either A or B.
(...)    Matches the RE inside the parentheses.
         The contents can be retrieved or matched later in the string.
(?:...)  Non-grouping version of regular parentheses.
(?i)     Perform case-insensitive matching.