Data set qualifier indexing function

The data set qualifier indexing function lets you index the &DSN and &MEMN variables (for accessing particular qualifiers):
&DSN(1)
first qualifier of the data set name
&DSN(3)
third qualifier of the data set name
&DSN(&NQUAL)
last qualifier of the data set name
&MEMN(1)
first qualifier of the object name
&MEMN(2)
second qualifier of the object name
&MEMN(&MEMNQUAL)
last qualifier of the object name

The only accepted values for indexes are numbers (1 through 22) and the read-only variables, &NQUAL and &MEMNQUAL.