Hi haukex; I've created an account so that I can edit things going forward, but since I cannot edit the original post, please forgive posting the full code in a reply: 
use strict;
use warnings;
use diagnostics;

use Text::CSV_XS;
use File::Find;
use File::Slurp qw(edit_file);
use List::Util qw(uniq);

my $spreadsheet = Text::CSV_XS->new ({ binary => 1, auto_diag => 1 });

# Consume the first argument (the spreadsheet input) and push its
# contents to an array of arrays.
open my $fh, "<", $ARGV[0];
my @table;
while (my $row = $spreadsheet->getline($fh)) {
    push @table, $row;
}
close $fh;

# Sort the array-of-arrays by the length of the 
# first element of each subarray (our 'keys') such 
# that the longest key comes first, and the
# shortest comes last. Then sort alphabetically.
@table = sort { length $b->[0] <=> length $a->[0] || $a->[0] cmp $b->[
+0] } @table; 

# CSVs are received from another department with 
# three columns, where the second denotes part of 
# speech. This isn't needed for this operation, so 
# discard it.
for my $row (@table) {
    splice(@$row,1,1);
    $row->[0] = quotemeta($row->[0]);
}

my @rows_to_cull = ();

# Pairwise comparison of rows to detect duplicate keys. 
# Sort having been performed earlier, only pairwise comparisons
# of adjacent rows will result in matches.
for my $row_a (0..$#table) {
    my $key = $table[$row_a]->[0];
    my @values = $table[$row_a]->[1];

    for my $row_b ($row_a+1..$#table) {
        if ( $table[$row_a]->[0] eq $table[$row_b]->[0] ) {
            push @values, $table[$row_b]->[1];
            $table[$row_a]->[1] = \@values;
            push @rows_to_cull, $row_b;
        }
        else {
            last;
        }
    }
}

# Convert the array to a hash to ensure uniqueness, 
# then back to an array for traversal, sorting the 
# array in descending numeric order so removal of 
# earlier rows doesn't interfere with indexing for 
# later rows.
my %cull_hash = map { $_ => 1 } @rows_to_cull;
my @cull_array = keys %cull_hash;
@cull_array = sort { $b <=> $a } @cull_array;

for (@cull_array) {
splice(@table,$_,1);
}

# Loop which ensures the uniqueness of elements in the 
# replacement candidate arrays.
for my $row (0..$#table) {
    my $replacement = $table[$row]->[1];
    if (ref($replacement) eq 'ARRAY' && length $replacement > 1) {
        my @unique = uniq(@$replacement);
        $table[$row]->[1] = \@unique;
    }
}

# The following takes the second argument from the 
# command line as the directory to operate on. It 
# also identifies a filter subroutine to exclude 
# non-documentation files from the checks, and a 
# subroutine that will actually do the search-and-replace.
find({ 
    preprocess => \&filter, 
    wanted => \&search_and_replace 
    }, 
    $ARGV[1]
);

sub filter {
    return grep { -d or (-f and ( /\.txt$/ or /\.rst$/ or /\.yaml$/))}
+ @_;
}

# Main loop

sub search_and_replace {
      open my $target_file, "<", $_;
      $| = 1;
      my $filename = $_;
      while (my $target_string = <$target_file>) {
        for my $row (@table) {
          my $search = $row->[0];
          my $replacement = $row->[1];
               
          if ((lc $target_string) =~ (lc $search)) {
            print "Found $search in $filename in the following context
+:\n";
            print "$target_string\n";
            if (ref($replacement) eq 'ARRAY' && length $replacement > 
+1) {
              print "Choose a replacement candidate by typing the appr
+opriate number, or else type '0' to skip.\n";
              my $count = 1;
              for my $value (@$replacement) {
                print "$count\) $value\n";
                  $count++;
              }
              my $choice = <STDIN>;
              if ($choice >= 1 && $choice <= (length $replacement)) {
                my $replace_choice = $replacement->[$choice];
                edit_file { s/$search/$replace_choice/gi} $filename;
              }
              else {
                print "Skipping this occurrence without replacing.\n";
              }
            }
            else {
              print "Confirm replacement with $replacement by typing y
+, or skip by typing any other key.\n";
              my $choice = <STDIN>;
              if ($choice eq 'y' || 'Y') {
                edit_file { s/$search/$replacement/gi } $filename;
              }
              else {
                print "Skipping this occurrence without replacing.\n";
              }
            }
          }
        }
      }
      close $target_file;
}

[download]
As for the input, here are some example rows from the CSV file itself, pre-sorted: 
whitelist entries,Noun,access list entries
IP whitelist,Noun,IP access list
IP whitelist entries,Noun,IP access list entries
whitelist,Adjective,allow
whitelist,Noun,access list
whitelist,Noun,access-list
whitelist,Verb,allow
your whitelist,Noun,your access list

[download]
As far as output goes, the sort should (and currently does) result in an entry like 'IP whitelist' being checked for before 'whitelist' itself, and 'IP whitelist entries' before 'IP whitelist; so I would expect that after I confirm wanting to replace 'IP whitelist entries' with 'IP access list entries', I would NOT be subsequently prompted to replace 'IP whitelist' within that instance of 'IP whitelist entries', because 'whitelist' would have already been replaced there. Similarly, I wouldn't want to be prompted to replace 'whitelist' alone in that spot for the same reason. Please let me know what more might be needed. I have started looking at the tutorial you linked and it seems promising.

EDIT: Corrected formatting errors due to copy-pasting code block with long lines.

In reply to Re^2: Immediately writing the results of search-and-replace by elemkeh
in thread Immediately writing the results of search-and-replace by Anonymous Monk

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