Perl finding duplicates (polishing up the existing code) - perl

Question

Hey All below is my code:
#!/bin/usr/perl
#words = ();
#dup = ();
print "Please enter your query sentence:\n";
$input = <STDIN>;
chomp $input;
#words = split(/ /, $input);
#sort = sort { "\L$a" cmp "\L$b" } #words;
for $n ( 0..$#sort ) {
if (lc $sort[$n] eq lc $sort[($n+1)]) {
push (#dup, $sort[$n]);
}
else {
$n+=1;
}
}
if ( #dup == () ) {
print "There are no duplicates in the query sentence.\n";
}
else {
print "#dup \n";
}
The problem I am having is if the word appears more than twice it appears in #dup for each additional occurrence. How do I fix this? Thanks in advance for your help!

Answer 1

It would be much simpler to use a Hash, which will still allow you to track duplicates and saves you from needing to presort your Array:
use strict;
use warnings;
print "Please enter your query sentence:\n";
my $input = <STDIN>;
chomp $input;
my #words = split /\s+/, $input;
my %unique_elems;
for my $word ( #words ) {
$unique_elems{$word}++;
}
if ( scalar keys %unique_elems == scalar #words ) {
print "There are no duplicates in the query sentence.\n";
}
else {
my #dups = grep { $unique_elem{$_} > 1 } keys %unique_elems;
print join ',', #dups;
print "\n";
}
A couple notes:
You should always use strict; use warnings; at the top of your scripts, it will save you more time than you would think
You should be using my to declare lexical variables instead of declaring globals

Answer 2

print "Please enter your query sentence:\n";
$input = <STDIN>;
chomp $input;
my #words = split /\s+/, $input;
my %words;
foreach my $word(#words) {
$words{lc($word)}++;
}
my #dup = grep {$words{$_} > 1} keys %words;
if (#dup == 0) {
print "There are no duplicates in the query sentence.\n";
}
else {
print "#dup \n";
}

Answer 3

Use this:
#!/bin/usr/perl
#words = ();
#dup = ();
print "Please enter your query sentence:\n";
$input = <STDIN>;
chomp $input;
#words = split(/ /, $input);
#sort= sort {"\L$a" cmp "\L$b"}#words;
%hash;
for $n (0..$#sort) {
if (lc $sort[$n] eq lc $sort[($n+1)]) {
if(!defined $hash{$sort[$n]}) {
push (#dup, $sort[$n]);
$hash{$sort[$n]}=1;
}
}
else {$n+=1;}
}
if (#dup==()){print "There are no duplicates in the query sentence.\n";}
else {print "#dup \n";}
just defined an additional hash %hash to keep the unique entries in the array.