I also like to point out that in the input file the keyword will be declared as below
in reply to Re^2: Checking value of an extracted variable
in thread Checking value of an extracted variable
OPT: SEL_BLOCK [
some text to be copied to output file
if SEL_BLOCK = 1
SEL_BLOCK will be defined in a config file which can be included in the perl script. The script will have visibilty of the value of SEL_BLOCK and take appropriate actions(copying contents from input to output file).