#!/usr/bin/perl -w

use strict;

my $script = "http://localhost/cgi-bin/test.pl";
my $file   = "/tmp/data.txt";

use CGI;
my $q = new CGI;
print $q->header();

if ( $q->param('delete') ) {
    my @deletions = modify_file();
    show_done_page(@deletions);
    show_form();
} else {
    show_form();
}
exit;

#### SUBS ####

sub show_form {
    my @lines = get_file($file);
    # remove newlines;
    chomp (@lines);
    my @data = map { [ split ':', $_ ] } @lines;
    my $html = join "\n", map {qq!<p><input type="checkbox" name="delete" value="$_->[0]">$_->[0]:$_->[1]! } @data;
    print <<HTML;
<form name="del" method="POST" action="$script"> 
$html
<input type="Submit" name="Submit" value="Delete"> 
HTML
}

sub get_file {
    my $file = shift;
    open FILE, $file or die_nice("Could not open $file, Perl says $!");
    my @lines = <FILE>;
    close FILE;
  return @lines;
}

sub write_file {
    my $file = shift;
    open FILE, ">$file" or die_nice("Could not write $file, Perl says $!");
    print FILE @_;
    close FILE;
}

sub modify_file {
    my @deletions = $q->param('delete');
    my $re = join '|', map { quotemeta } @deletions;
    $re = qr/^($re):/;
    my @lines = get_file($file);
    my @ok_lines = grep { not /$re/ } @lines;
    write_file($file, @ok_lines);
  return @deletions;
}

sub show_done_page {
    my @deletions = @_;
    my $html = join "\n", map { "$_<br>" } @deletions;
    print "<p>Deleted these entries:\n<p>$html";
}

sub die_nice {
    my $error = shift;
    print "Sorry an error occurred: $error";
  exit;
}