#!/usr/bin/env perl
#
# previsprefix - print similar files
#
# $Id$

# on a sorted list of pathnames, prints the ones
# that differ only in the directoryless pathname

use warnings;
use strict;

my %printed          = ();
my %slashes          = ();
my %occurring_prefix = ();

$| = 1;    # flush output after every line

my $prev = '';
$slashes{$prev} = 0;

while (<>)
{
  chomp;

  next if $_ eq $prev;

  while ( substr( $_, 0, length($prev) ) ne $prev )
  {
    $prev = $occurring_prefix{$prev};
  }

  $occurring_prefix{$_} = $prev;
  $slashes{$_}          = y#/#/#;

  if ( $prev ne '' && $slashes{$_} eq $slashes{$prev} )
  {
    # found a match - print it
    if ( !exists $printed{$prev} )
    {
      print $prev . "\n";
      $printed{$prev} = 1;
    }
    print $_ . "\n";
    $printed{$_} = 1;
  }

  $prev = $_;
}