Personally, I would slurp the file into an array, and then create a new array for your expected output. then I would loop through the original array comparing the second and third element, and if $_1 gt $_2 then push what data you need to the final array like:

for(@input){
    if($_[1] gt $_[2]){
    push (@output, "$_[0] $_[2] $_[1] $[3] +");
}

print "$_\n" for @output;
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EDIT: Sorry for the confusion, you will need to split the element if you do it this way, please take this code into consideration:

use strict;
use warnings;

my @input;
my @output;

while (<DATA>) {
    push @input, $_;
}
for (@input) {
    my @temp = split( /\s+/, $_ ); # you split on a delimiter, which i
+s 1 or more spaces in this case

    if ( $temp[1] gt $temp[2] ) {
        push( @output, "$temp[0] $temp[2] $temp[1] $temp[3] +" );
    }
    else {
        push @output, "$temp[0] $temp[1] $temp[2] $temp[3]";
    }
}

print "$_\n" for @output

__DATA__
red 15 2 smith
blue 4 10 walter
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The reason I posted the code is because I earlier told you to do it a certain way, without also telling you that you would need to use the split function and create a temporary array to store the results from the split.