dominick_t:

I'd suggest running it under the debugger (perl -d script.pl) and examine the interesting bits and/or the bits you don't understand. The debugger isn't terribly difficult to use, and it's the easiest way to suss out the details you don't understand yet.

$ perl -d pm_135391.pl
Loading DB routines from perl5db.pl version 1.49_001
Editor support available.

Enter h or 'h h' for help, or 'man perldebug' for more help.

main::(pm_135391.pl:1): while (<DATA>) {
  DB<1> n
main::(pm_135391.pl:2):   chomp;
  DB<1> p "<$_>"
<Abby
>
[download]

So here, we started the program under the debugger, executed the first statement (loading $_ from <DATA>), then displayed the value using the p command. (I used "<$_>" to put delimiters around the value, so you can see that it has end-of-line characters in it.

  DB<2> n
main::(pm_135391.pl:3):   my $key = lc $_;
  DB<2> n
main::(pm_135391.pl:4):   next if $seen{$key}++;
  DB<2> n
main::(pm_135391.pl:5):   my $signature = join "", sort split //, $key
+;
  DB<2> x %seen
0  "abby \cM"
1  1
[download]

Here, we executed the next three lines to chomp the value, make the $key value, and add $key to the %seen hash. Then I used the x command to display the %seen hash, so you can see what's in it.

  DB<3> n
main::(pm_135391.pl:6):   push @{$words{$signature}}, $_;
  DB<3> x $signature
0  "\cM abby"
  DB<4> h
List/search source lines:               Control script execution:
  l [ln|sub]  List source code            T           Stack trace
  - or .      List previous/current line  s [expr]    Single step [in 
+expr]
  v [line]    View around line            n [expr]    Next, steps over
+ subs
  f filename  View source in file         <CR/Enter>  Repeat last n or
+ s
  /pattern/ ?patt?   Search forw/backw    r           Return from subr
+outine
  M           Show module versions        c [ln|sub]  Continue until p
+osition
Debugger controls:                        L           List break/watch
+/actions
  o [...]     Set debugger options        t [n] [expr] Toggle trace [m
+ax depth] ][trace expr]
  <[<]|{[{]|>[>] [cmd] Do pre/post-prompt b [ln|event|sub] [cnd] Set b
+reakpoint
  ! [N|pat]   Redo a previous command     B ln|*      Delete a/all bre
+akpoints
  H [-num]    Display last num commands   a [ln] cmd  Do cmd before li
+ne
  = [a val]   Define/list an alias        A ln|*      Delete a/all act
+ions
  h [db_cmd]  Get help on command         w expr      Add a watch expr
+ession
  h h         Complete help page          W expr|*    Delete a/all wat
+ch exprs
  |[|]db_cmd  Send output to pager        ![!] syscmd Run cmd in a sub
+process
  q or ^D     Quit                        R           Attempt a restar
+t
Data Examination:     expr     Execute perl code, also see: s,n,t expr
  x|m expr       Evals expr in list context, dumps the result or lists
+ methods.
  p expr         Print expression (uses script's current package).
  S [[!]pat]     List subroutine names [not] matching pattern
  V [Pk [Vars]]  List Variables in Package.  Vars can be ~pattern or !
+pattern.
  X [Vars]       Same as "V current_package [Vars]".  i class inherita
+nce tree.
  y [n [Vars]]   List lexicals in higher scope <n>.  Vars same as V.
  e     Display thread id     E Display all thread ids.
For more help, type h cmd_letter, or run man perldebug for all docs.
[download]

Then, I decided I showed you enough ;^) and had it print the help page. Have fun with it!

...roboticus

When your only tool is a hammer, all problems look like your thumb.