Имя переменной в shell

Из man bash:
${parameter##word}
The word is expanded to produce a pattern just as in pathname expansion. If the pattern matches
the beginning of the value of parameter, then the result of the expansion is the expanded value
of parameter with the shortest matching pattern (the ``#'' case) or the longest matching pattern
(the ``##'' case) deleted. If parameter is @ or *, the pattern removal operation is applied to
each positional parameter in turn, and the expansion is the resultant list. If parameter is an
array variable subscripted with @ or *, the pattern removal operation is applied to each member
of the array in turn, and the expansion is the resultant list.


А вообще похоже конструкция означает то же (почти), что и PRIMER=`basename $0` - т.е. получает последний элемент строки с разделителем "/".

Спа. Только там интерпретатор sh, а не bash. Но результат тот же.)