READF cannot find a column label

If a column label is used with the READF command instead of the column number (see §) and READF fails, e.g. :

PONGO> readf myfile.dat xcol=1 ycol=3 zcol="ZCOL"
File: /disk/scratch/jbloggs/plots/myfile.dat
XCOL - 1 is column number 1.
YCOL - 3 is column number 3.
!! ZCOL incorrectly specified as ZCOL.
!  READF: Data could not be read.

then either the data file does not have column labels or the incorrect column label has been used. It is of particular significance here that the column labels are case-sensitive. In fact, JBLOGGS found that the column label for his ZCOL data was Zcol:

PONGO> readf myfile.dat xcol=1 ycol=3 zcol="Zcol"
File: /disk/scratch/jbloggs/plots/myfile.dat
XCOL - 1 is column number 1.
YCOL - 3 is column number 3.
ZCOL - Zcol is column number 5.
EXCOL - 0 is column number 0.
EYCOL - 0 is column number 0.
LABCOL - 0 is column number 0.
SYMCOL - 0 is column number 0.
42 data points read.
PONGO>