Returns the number of the program line where the last error happened
Implemented by: decbasic, msatari, level2, BBC, GWBASIC, MSX, bwbasic, bw32, QBasic, VBDOS, FreeBASIC
With variations:
Also written as:
GW-BASIC's official documentation lists ERL as a system variable instead of a function, but it apparently does not change its usage.
Predictably, in the structured MS-QuickBASIC family, ERL is always 0 if the program is not written with line numbers.