column relationship value num_or_string filter_or_append order
a      <=           0.3   num           filter           1
b      eq           abc   string        append           3
c      <=           0.3   num           filter           2

##</code><code>##

a     b     c
0.2   abc   0.3
0.1   abd   0.3
0.4   abe   0.2
0.1   abc   0.5
0.7   abt   0.7
0.1   abd   0.8

##</code><code>##

#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;

#link to input file from command line - 2 arguments or error displayed; Set to respective variables
@ARGV == 2 or die "Invalid number or arguments. Please re-run program and supply as arguments: \n1) the filter file and \n2) the input file.";
my ($filter_file, $input_file) = @ARGV;

open (FILTER,"$filter_file");
my @filter;

<FILTER>; # read one line from the file [HEADERS]

while (<FILTER>)
{ # read other lines
	chomp; # remove "\n" from the end of the line
	push @filter,[(split /\t/,$_)]; # create an array of the line by splitting it by <TAB>, make a reference of it and push the reference to the @filter array
	close $filter_file if eof;
}


@filter = sort { $a->[5] <=> $b->[5] } @filter; # sort the array 

#PRINTS REFERENCES TO ARRAY FROM LEAST TO GREATEST REGARDING 'ORDER' COLUMN
print Dumper \@filter; #### For Debugging Purposes
my $num_elements = (@filter-1); #Number of elements in array - will be used to control loop when comparisons take place later in code


##</code><code>##

open (IN, "$input_file") or die "Cannot open file: $!";

#variables
my $x=0;
my @keys;
my @holder;
my @array_hash;
my $blank = "-";
my $numerical_value = "num";
my $string_value = "string";
my $filter_data = "filter";
my $append = "append";

open (OUTFILE, ">>OUTPUT_$input_file") or die "Cannot create an output file: $!";

while(my $line = <IN>)
{
        chomp($line);
        $x++;
        if ($x==1)
        {
                print OUTFILE $line, "\n";
                (@keys)=split(/\t/, $line);
        }
        else
        {
                my $y=0;
                (@holder) = split(/\t/, $line);
                my %hash;
                for my $column (@holder)
                {
                        $hash{$keys[$y]}=$column;
                        $y++;
                }


##</code><code>##

if ((eval "$hash{$filter[0]->[0]} $filter[0]->[1] $filter[0]->[2]") && (eval "'$hash{$filter[1]->[0]}' $filter[1]->[1] '$filter[1]->[2]'") && (eval "$hash{$filter[2]->[0]} $filter[2]->[1] $filter[2]->[2]"))
{
    print OUTFILE $line, "\n";
}

##</code><code>##

	for(my $c = 0; $c <= $num_elements; $c++)
	{
		if($hash{$filter[$c]->[4]} eq $filter_data)
		{
			if (exists($hash{$filter[$c]->[0]}))
			{
				if($hash{$filter[$c]->[3]} eq $numerical_value)
				{
#					#process filtering for numerical value
					if ((eval "$hash{$filter[$c]->[0]} $filter[$c]->[1] $filter[$c]->[2]"))
					{
						print OUTFILE $line, "\n";
					}
				}
			}
			else
			{
				print "COLUMN NAME DOES NOT EXIST. CHECK FILTER FILE FOR ANY POSSIBLE ERRORS AND RE-RUN PROGRAM. PROGRAM WILL NOW TERMINATE.", "\n";
				exit 0;
			}
		}
	}