sub duplicateLines { my ($filename) = @_; open(FILE, $filename) or die; %lines = (); my $lineCount = 1; my $duplicate = 0; while (chomp($line =)) { if (exists($lines{$line})) { print "lines $lines{$line} and $lineCount are duplicates\n"; $duplicate = 1; } else { $lines{$line} = $lineCount; } $lineCount++; } return $duplicate; }