How to get last duplicate line from file using perl - perl

Question

I'd like to get the last entry of a duplicate line from a file.
The basis for duplicate checking would be the first element from a csv.
The duplicates may or may not be adjacent.
Input file:
971~11
972~12
973~11
974~11
972~11
Expected output:
971~11
973~11
974~11
972~11
I'm not looking for a perl one-liner as I intend to write this as
a subroutine.
Thanks!
PS:
I have modified this code from somewhere, but this just removes the duplicates
#!/usr/bin/perl -w
while (<STDIN>) { push (#lines, $_); }
print "-\n";
foreach my $i (#lines)
{
#newline = split(/\||~/, $i);
if (scalar(grep{ /$newline[0]/ } #lines) == 1)
{
print $i;
}
}

Answer 1

If the output order doesn't matter, the easiest way to do this is to use a hash to do the duplicate removal. Something like the following:
#!/usr/bin/perl -w
use strict;
sub printlast(#) {
my %dedup;
foreach my $line (#_) {
my $a = (split(/\||~/, $line))[0];
$dedup{$a} = $line;
}
print $dedup{$_} for keys %dedup; # or sort keys %dedup for prettier output
}
my #lines;
while (<STDIN>) { push (#lines, $_); }
print "-\n";
printlast(#lines);

Answer 2

When looking to dedup, it's almost always best to use a hash.
Here's something similar to the accepted answer (since #Mat beat me to it)
#!/usr/bin/env perl -lw
use Data::Dumper; $Data::Dumper::Indent = 1;
my %seen;
while (<DATA>) {
chomp;
my #fields = split('~');
$seen{$fields[0]} = $fields[1];
}
my #output;
while (my ($k,$v) = each %seen) {
push #output, join('~', $k, $v);
}
print Dumper \#output;
__DATA__
971~11
972~12
973~11
974~11
972~11