I'd be keeping track of the keys when you're assigning to the definition hash. That is, keep a separate hash with duplicate keys. There is probably a more efficient way to do this, but some random puttering around while I'm waiting for my work script to finish:
#!/usr/bin/perl
use strict;
use warnings;
my (%hash, %dup_hash);
# Minor tweak to read from DATA rather than a file
while (my $line = <DATA>) {
chomp($line);
my ($enu, $deu) = split /\t/, $line;
$hash{$enu} = $deu;
# Keep a list of all duplicate values
push @{$dup_hash{$deu}}, $enu;
}
for my $key (keys %hash) {
print "$key\n";
}
for my $value (values %hash) {
print "$value\n";
}
print "\nDuplicate definitions:\n";
for my $deu (keys %dup_hash) {
if (scalar @{$dup_hash{$deu}} > 1) {
for my $en (@{$dup_hash{$deu}}) {
print "$deu => $en\n";
}
print "\n";
}
}
__DATA__
Retire a document Dokument deaktivieren
Remove a document from the knowledge base Dokument aus der Knowledg
+e Base entfernen
Promote document retirement Dokument deaktivieren
Document Expired Dokument abgelaufen
Gives the output:
Remove a document from the knowledge base
Document Expired
Promote document retirement
Retire a document
Dokument aus der Knowledge Base entfernen
Dokument abgelaufen
Dokument deaktivieren
Dokument deaktivieren
Duplicate definitions:
Dokument deaktivieren => Retire a document
Dokument deaktivieren => Promote document retirement
Edit: Renamed some of the variables to accurately reflect their contents. Second edit Pretty much the same thing as what JavaFan has, just different syntactical approach.