Returns the line number of the statement that caused the error or the closest line number before the error-causing statement.
ERL
ERL returns only line numbers. It does not return line labels. If you are not using line numbers, ERL returns 0.
100 PRINT 1/0
1000 Handler:
1010   PRINT "Error processing at line"; ERL
1020   PRINT "Error number"; ERR
1030   RESUME
Running this program produces the following:
Error processing at line 100
Error number 11