r.biswas:

I'd suggest writing a subroutine to read all your configurations into an array, and then when processing the input file you can simply load the current configuration. Something like:

my @configurations;
load_configurations("config_file");

open my $FH, '<', $input_fname or die "Can't open $input_fname: $!";
while (<$FH>) {
    my @config_vars;
    ... parse out an input entry ...
    @config_vars = @$configurations[$configuration_ID];
    ... code to process input using configuration variables...
}

sub load_configurations {
    my $fname = shift;
    open my $FH, '<', $fname or die "Can't open $fname: $!";
    while (<$FH>) {
        my @config_vars;
        ... parse out a configuration...
        $configurations[$configuration_ID] = [ @config_vars ];
    }
}
[download]

This way, you have all the configurations at your fingertips, and you can process each input entry with a different configuration, if desired.

...roboticus

When your only tool is a hammer, all problems look like your thumb.