note
roboticus
<p>[dominick_t]:</p>
<p>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.</p>
<c>
$ 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
>
</c>
<p>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.</p>
<c>
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
</c>
<p>Here, we executed the next three lines to chomp the value, make the $key value, and add $key to the %seen hash. Then I used the x command to display the %seen hash, so you can see what's in it.</p>
<c>
DB<3> n
main::(pm_135391.pl:6): push @{$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 subroutine
M Show module versions c [ln|sub] Continue until position
Debugger controls: L List break/watch/actions
o [...] Set debugger options t [n] [expr] Toggle trace [max depth] ][trace expr]
<[<]|{[{]|>[>] [cmd] Do pre/post-prompt b [ln|event|sub] [cnd] Set breakpoint
! [N|pat] Redo a previous command B ln|* Delete a/all breakpoints
H [-num] Display last num commands a [ln] cmd Do cmd before line
= [a val] Define/list an alias A ln|* Delete a/all actions
h [db_cmd] Get help on command w expr Add a watch expression
h h Complete help page W expr|* Delete a/all watch exprs
|[|]db_cmd Send output to pager ![!] syscmd Run cmd in a subprocess
q or ^D Quit R Attempt a restart
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 inheritance 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.
</c>
<p>Then, I decided I showed you enough ;^) and had it print the help page. Have fun with it!</p>
<p>...[roboticus]</p>
<p><i>When your only tool is a hammer, all problems look like your thumb.</i></p>
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