The option ‘-l[mmm[:nnn]]’ echoes the input lines constructed by the input driver between lines mmm and nnn. Missing nnn means echo to the end of file. Missing mmm means echo from the beginning.
This option is useful as a debugging tool (usually by the system developer). It is often used to verify that the input driver is inserting semicolons correctly. For FORTRAN–77, it is also useful to verify that comments are being processed correctly.