Is there any way to replace multiple strings in a string?
For example, I have the string hello world what a lovely day and I want to replace what and lovely with something else..
$sentence = "hello world what a lovely day";
#list = ("what", "lovely"); # strings to replace
#replist = ("its", "bad"); # strings to replace with
($val = $sentence) =~ "tr/#list/#replist/d";
print "$val\n"; # should print "hello world its a bad day"..
Any ideas why it's not working?
Thanks.
First of all, tr doesn't work that way; consult perldoc perlop for details, but tr does transliteration, and is very different from substitution.
For this purpose, a more correct way to replace would be
# $val
$val =~ s/what/its/g;
$val =~ s/lovely/bad/g;
Note that "simultaneous" change is rather more difficult, but we could do it, for example,
%replacements = ("what" => "its", "lovely" => "bad");
($val = $sentence) =~ s/(#{[join "|", keys %replacements]})/$replacements{$1}/g;
(Escaping may be necessary to replace strings with metacharacters, of course.)
This is still only simultaneous in a very loose sense of the term, but it does, for most purposes, act as if the substitutions are done in one pass.
Also, it is more correct to replace "what" with "it's", rather than "its".
Well, mainly it's not working as tr///d has nothing to do with your request (tr/abc/12/d replaces a with 1, b with 2, and removes c). Also, by default arrays don't interpolate into regular expressions in a way that's useful for your task. Also, without something like a hash lookup or a subroutine call or other logic, you can't make decisions in the right-hand side of a s/// operation.
To answer the question in the title, you can perform multiple replaces simultaneously--er, in convenient succession--in this manner:
#! /usr/bin/env perl
use common::sense;
my $sentence = "hello world what a lovely day";
for ($sentence) {
s/what/it's/;
s/lovely/bad/
}
say $sentence;
To do something more like what you attempt here:
#! /usr/bin/env perl
use common::sense;
my $sentence = "hello world what a lovely day";
my %replace = (
what => "it's",
lovely => 'bad'
);
$sentence =~ s/(#{[join '|', map { quotemeta($_) } keys %replace]})/$replace{$1}/g;
say $sentence;
If you'll be doing a lot of such replacements, 'compile' the regex first:
my $matchkey = qr/#{[join '|', map { quotemeta($_) } keys %replace]}/;
...
$sentence =~ s/($matchkey)/$replace{$1}/g;
EDIT:
And to expand on my remark about array interpolation, you can change $":
local $" = '|';
$sentence =~ s/(#{[keys %replace]})/$replace{$1}/g;
# --> $sentence =~ s/(what|lovely)/$replace{$1}/g;
Which doesn't improve things here, really, although it may if you already had the keys in an array:
local $" = '|';
$sentence =~ s/(#keys)/$replace{$1}/g;
I'm looping through an array, and I want to test if an element is found in another array.
In pseudo-code, what I'm trying to do is this:
foreach $term (#array1) {
if ($term is found in #array2) {
#do something here
}
}
I've got the "foreach" and the "do something here" parts down-pat ... but everything I've tried for the "if term is found in array" test does NOT work ...
I've tried grep:
if grep {/$term/} #array2 { #do something }
# this test always succeeds for values of $term that ARE NOT in #array2
if (grep(/$term/, #array2)) { #do something }
# this test likewise succeeds for values NOT IN the array
I've tried a couple different flavors of "converting the array to a hash" which many previous posts have indicated are so simple and easy ... and none of them have worked.
I am a long-time low-level user of perl, I understand just the basics of perl, do not understand all the fancy obfuscated code that comprises 99% of the solutions I read on the interwebs ... I would really, truly, honestly appreciate any answers that are explicit in the code and provide a step-by-step explanation of what the code is doing ...
... I seriously don't grok $_ and any other kind or type of hidden, understood, or implied value, variable, or function. I would really appreciate it if any examples or samples have all variables and functions named with clear terms ($term as opposed to $_) ... and describe with comments what the code is doing so I, in all my mentally deficient glory, may hope to possibly understand it some day. Please. :-)
...
I have an existing script which uses 'grep' somewhat succesfully:
$rc=grep(/$term/, #array);
if ($rc eq 0) { #something happens here }
but I applied that EXACT same code to my new script and it simply does NOT succeed properly ... i.e., it "succeeds" (rc = zero) when it tests a value of $term that I know is NOT present in the array being tested. I just don't get it.
The ONLY difference in my 'grep' approach between 'old' script and 'new' script is how I built the array ... in old script, I built array by reading in from a file:
#array=`cat file`;
whereas in new script I put the array inside the script itself (coz it's small) ... like this:
#array=("element1","element2","element3","element4");
How can that result in different output of the grep function? They're both bog-standard arrays! I don't get it!!!! :-(
########################################################################
addendum ... some clarifications or examples of my actual code:
########################################################################
The term I'm trying to match/find/grep is a word element, for example "word123".
This exercise was just intended to be a quick-n-dirty script to find some important info from a file full of junk, so I skip all the niceties (use strict, warnings, modules, subroutines) by choice ... this doesn't have to be elegant, just simple.
The term I'm searching for is stored in a variable which is instantiated via split:
foreach $line(#array1) {
chomp($line); # habit
# every line has multiple elements that I want to capture
($term1,$term2,$term3,$term4)=split(/\t/,$line);
# if a particular one of those terms is found in my other array 'array2'
if (grep(/$term2/, #array2) {
# then I'm storing a different element from the line into a 3rd array which eventually will be outputted
push(#known, $term1) unless $seen{$term1}++;
}
}
see that grep up there? It ain't workin right ... it is succeeding for all values of $term2 even if it is definitely NOT in array2 ... array1 is a file of a couple thousand lines. The element I'm calling $term2 here is a discrete term that may be in multiple lines, but is never repeated (or part of a larger string) within any given line. Array2 is about a couple dozen elements that I need to "filter in" for my output.
...
I just tried one of the below suggestions:
if (grep $_ eq $term2, #array2)
And this grep failed for all values of $term2 ... I'm getting an all or nothing response from grep ... so I guess I need to stop using grep. Try one of those hash solutions ... but I really could use more explanation and clarification on those.
This is in perlfaq. A quick way to do it is
my %seen;
$seen{$_}++ for #array1;
for my $item (#array2) {
if ($seen{$item}) {
# item is in array2, do something
}
}
If letter case is not important, you can set the keys with $seen{ lc($_) } and check with if ($seen{ lc($item) }).
ETA:
With the changed question: If the task is to match single words in #array2 against whole lines in #array1, the task is more complicated. Trying to split the lines and match against hash keys will likely be unsafe, because of punctuation and other such things. So, a regex solution will likely be the safest.
Unless #array2 is very large, you might do something like this:
my $rx = join "|", #array2;
for my $line (#array1) {
if ($line =~ /\b$rx\b/) { # use word boundary to avoid partial matches
# do something
}
}
If #array2 contains meta characters, such as *?+|, you have to make sure they are escaped, in which case you'd do something like:
my $rx = join "|", map quotemeta, #array2;
# etc
You could use the (infamous) "smart match" operator, provided you are on 5.10 or later:
#!/usr/bin/perl
use strict;
use warnings;
my #array1 = qw/a b c d e f g h/;
my #array2 = qw/a c e g z/;
print "a in \#array1\n" if 'a' ~~ #array1;
print "z in \#array1\n" if 'z' ~~ #array1;
print "z in \#array2\n" if 'z' ~~ #array2;
The example is very simple, but you can use an RE if you need to as well.
I should add that not everyone likes ~~ because there are some ambiguities and, um, "undocumented features". Should be OK for this though.
This should work.
#!/usr/bin/perl
use strict;
use warnings;
my #array1 = qw/a b c d e f g h/;
my #array2 = qw/a c e g z/;
for my $term (#array1) {
if (grep $_ eq $term, #array2) {
print "$term found.\n";
}
}
Output:
a found.
c found.
e found.
g found.
#!/usr/bin/perl
#ar = ( '1','2','3','4','5','6','10' );
#arr = ( '1','2','3','4','5','6','7','8','9' ) ;
foreach $var ( #arr ){
print "$var not found\n " if ( ! ( grep /$var/, #ar )) ;
}
Pattern matching is the most efficient way of matching elements. This would do the trick. Cheers!
print "$element found in the array\n" if ("#array" =~ m/$element/);
Your 'actual code' shouldn't even compile:
if (grep(/$term2/, #array2) {
should be:
if (grep (/$term2/, #array2)) {
You have unbalanced parentheses in your code. You may also find it easier to use grep with a callback (code reference) that operates on its arguments (the array.) It helps keep the parenthesis from blurring together. This is optional, though. It would be:
if (grep {/$term2/} #array2) {
You may want to use strict; and use warnings; to catch issues like this.
The example below might be helpful, it tries to see if any element in #array_sp is present in #my_array:
#! /usr/bin/perl -w
#my_array = qw(20001 20003);
#array_sp = qw(20001 20002 20004);
print "#array_sp\n";
foreach $case(#my_array){
if("#array_sp" =~ m/$case/){
print "My God!\n";
}
}
use pattern matching can solve this. Hope it helps
-QC
1. grep with eq , then
if (grep {$_ eq $term2} #array2) {
print "$term2 exists in the array";
}
2. grep with regex , then
if (grep {/$term2/} #array2) {
print "element with pattern $term2 exists in the array";
}
Never done much programming -- been charged at work with manipulating the data from comment cards. Using perl so far I've got the database to correctly put its daily comments into an array. Comments are each one LINE of text within the database, so I just split the array on the line-break.
my #comments = split("\n", $c_data);
And yes, this being my first time programming, that took me wayyy too long to figure out.
At this point I now need to organize these array elements (is that what I should call them?) into their own separate scalars based on capitalized words (this is a behavior of the database, which was at one point corrupt).
Example of what two elements of the array look like:
print "$comments[0]\n";
This dining experience was GOOD blah blah blah.
or
print "$comments[1]\n";
Overall this was a BAD time and me and my blah blah.
These "good" or "bad" or "best" are already capitalized by the database the data came from.
What's the easiest way in Perl to get these lines into scalars from an array based on these capitalized words?
If I understand you correctly, you want to merge array elements that match a certain word. You can do it like this:
my #bad_comments = grep { /\bBAD\b/ } #comments;
my #good_comments = grep { /\bGOOD\b/ } #comments;
That way all 'good' and 'bad' comments go to each own array.
Now if you need to merge them into a scalar you'd want to join them (opposite of split):
my $bad_comments = join "\n", grep { /\bBAD\b/ } #comments;
my $good_comments = join "\n", grep { /\bGOOD\b/ } #comments;
Think hash table when you want to group data by arbitrary string keys. In this case, you have an array of GOOD comments and an array of BAD comments. What if you had an array of SO-SO comments? A strategy based on having array variables #good, #bad, #soso breaks down fast.
You have some ways to go before you can fully understand the code below:
#!/usr/bin/perl
use strict; use warnings;
use Regex::PreSuf;
my %comments;
my #types = qw( GOOD BAD ); # DRY
my $types_re = presuf #types;
while ( my $comment = <DATA> ) {
chomp $comment;
last unless $comment =~ /\S/;
# capturing match in list context returns captured strings
my ($type) = ( $comment =~ /($types_re)/ );
push #{ $comments{$type} }, $comment;
}
for my $type ( #types ) {
print "$type comments:\n";
for my $comment ( #{ $comments{$type} } ) {
print $comment, "\n";
}
}
__DATA__
This dining experience was GOOD blah blah blah.
Overall this was a BAD time and me and my blah blah.
You could use regular expressons, eg:
if ($comments[$i] =~ /GOOD/) {
# good comment
}
or more generally
if ($comments[$i] =~ /\b([A-Z]{2,})\b/) {
print "Comment: $1\n";
}
Here, \b means word boundary, () are used to extract captured text, [A-Z] represent a group of capital characters - capital letters, {2,} means that there have to be 2 or more characters defined by previous class.
I would store all your comments into a hash-of-arrays data structure, with the key being your capitalized word.
Here is a general solution to grab any capitalized word (assuming only one per comment), not just GOOD and BAD:
use strict;
use warnings;
my #comments = <DATA>;
chomp #comments;
my %data;
for (#comments) {
my $cap;
for (split) {
$cap = $_ if /^[A-Z]+$/;
}
if ($cap) { push #{ $data{$cap} }, $_ }
}
use Data::Dumper; print Dumper(\%data);
__DATA__
This is GOOD stuff
Here's some BAD stuff.
More of the GOOD junk.
Nothing here.
Here is the output:
$VAR1 = {
'BAD' => [
'Here\'s some BAD stuff.'
],
'GOOD' => [
'This is GOOD stuff',
'More of the GOOD junk.'
]
};
In my opinion, your best bet would be to create a disk-based database of some sort (SQLite?) that stores the comments and type as separate data.
Then use one of the other posted solutions to import your existing data into it.
The only problem here is that you need to learn Perl's DBI layer and a bit of SQL to use SQLite with Perl.
Not sure what you mean by "organize" and "based on".
If you mean produce a list of any capitalized words, each with a list of the lines containing that word (similar to toolic's solution, you could do this:
my %CAPS = ();
map {
my ($word) = /(\b[A-Z]+\b)/;
push( #{ $CAPS{$word} }, $_)
} #comments;
This will build a mapping of WORDS to things, and the things in this case are going to be lists of lines.
And you can refer to these lists as $CAPS{'GOOD'} or $CAPS{'BAD'}, or $CAPS{whatever}.
What? Perl Beautiful? Elegant? He must be joking!
It's true, there's some ugly Perl out there. And by some, I mean lots. We've all seen it.
Well duh, it's symbol soup. Isn't it?
Yes there are symbols. Just like 'math' has 'symbols'. It's just that we programmers are more familiar with the standard mathematical symbols. We grew to accept the symbols from our mother languages, whether that be ASM, C, or Pascal. Perl just decided to have a few more.
Well, I think we should get rid of all the unnecessary symbols. Makes the code look better.
The language for doing so already exists. It's called Lisp. (and soon, perl 6.)
Okay, smart guy. Truth is, I can already invent my own symbols. They're called functions and methods. Besides, we don't want to reinvent APL.
Oh, fake alter ego, you are so funny! It's really true, Perl can be quite beautiful. It can be quite ugly, as well. With Perl, TIMTOWTDI.
So, what are your favorite elegant bits of Perl code?
Perl facilitates the use of lists/hashes to implement named parameters, which I consider very elegant and a tremendous aid to self-documenting code.
my $result = $obj->method(
flux_capacitance => 23,
general_state => 'confusion',
attitude_flags => ATTITUDE_PLEASANT | ATTITUDE_HELPFUL,
);
My favourite pieces of elegant Perl code aren't necessarily elegant at all. They're meta-elegant, and allow you to get rid of all those bad habits that many Perl developers have slipped into. It would take me hours or days to show them all in the detail they deserve, but as a short list they include:
autobox, which turns Perl's primitives into first-class objects.
autodie, which causes built-ins to throw exceptions on failure (removing most needs for the or die... construct). See also my autodie blog and video).
Moose, which provide an elegant, extensible, and correct way of writing classes in Perl.
MooseX::Declare, which provides syntaxic aweseomeness when using Moose.
Perl::Critic, your personal, automatic, extensible and knowledgeable code reviewer. See also this Perl-tip.
Devel::NYTProf, which provides me the most detailed and usable profiling information I've seen in any programming language. See also Tim Bunce's Blog.
PAR, the Perl Archiver, for bundling distributions and even turning whole programs into stand-alone executable files. See also this Perl-tip.
Perl 5.10, which provides some stunning regexp improvements, smart-match, the switch statement, defined-or, and state variables.
Padre, the only Perl editor that integrates the best bits of the above, is cross-platform, and is completely free and open source.
If you're too lazy to follow links, I recently did a talk at Linux.conf.au about most of the above. If you missed it, there's a video of it on-line (ogg theora). If you're too lazy to watch videos, I'm doing a greatly expanded version of the talk as a tutorial at OSCON this year (entitled doing Perl right).
All the best,
Paul
I'm surprised no one mentioned the Schwartzian Transform.
my #sorted =
map { $_->[0] }
sort { $a->[1] <=> $b->[1] }
map { [ $_, expensive_func($_) ] }
#elements;
And in the absence of a slurp operator,
my $file = do { local $/; readline $fh };
Have a list of files the user wants your program to process? Don't want to accidentally process a program, folder, or nonexistent file? Try this:
#files = grep { -T } #files;
And, like magic, you've weeded out all the inappropriate entries. Don't want to ignore them silently? Add this line before the last one:
warn "Not a file: $_" foreach grep { !-T } #files;
Prints a nice warning message for every file that it can't process to standard error. The same thing without using grep would look like this:
my #good;
foreach(#files) {
if(-T) {
push #good, $_;
} else {
warn "Not a file: $_";
}
}
grep (and map) can be used to make code shorter while still keeping it very readable.
The "or die" construct:
open my $fh, "<", $filename
or die "could not open $filename: $!";
The use of qr// to create grammars:
#!/usr/local/ActivePerl-5.10/bin/perl
use strict;
use warnings;
use feature ':5.10';
my $non_zero = qr{[1-9]};
my $zero = qr{0};
my $decimal = qr{[.]};
my $digit = qr{$non_zero+ | $zero}x;
my $non_zero_natural = qr{$non_zero+ $digit*}x;
my $natural = qr{$non_zero_natural | $zero}x;
my $integer = qr{-? $non_zero_natural | $zero}x;
my $real = qr{$integer (?: $decimal $digit)?}x;
my %number_types = (
natural => qr/^$natural$/,
integer => qr/^$integer$/,
real => qr/^$real$/
);
for my $n (0, 3.14, -5, 300, "4ever", "-0", "1.2.3") {
my #types = grep { $n =~ $number_types{$_} } keys %number_types;
if (#types) {
say "$n is of type", #types == 1 ? " ": "s ", "#types";
} else {
say "$n is not a number";
}
}
Anonymous subroutines used to factor out duplicate code:
my $body = sub {
#some amount of work
};
$body->();
$body->() while $continue;
instead of
#some amount of work
while ($continue) {
#some amount of work again
}
Hash based dispatch tables:
my %dispatch = (
foo => \&foo,
bar => \&bar,
baz => \&baz
);
while (my $name = iterator()) {
die "$name not implemented" unless exists $dispatch{$name};
$dispatch{$name}->();
}
instead of
while (my $name = iterator()) {
if ($name eq "foo") {
foo();
} elsif ($name eq "bar") {
bar();
} elsif ($name eq "baz") {
baz();
} else {
die "$name not implemented";
}
}
Three-line classes with constructors, getter/setters and type validation:
{
package Point;
use Moose;
has ['x', 'y'] => (isa => 'Num', is => 'rw');
}
package main;
my $point = Point->new( x => '8', y => '9' );
$point->x(25);
A favorite example of mine is Perl's implementation of a factorial calculator. In Perl 5, it looks like so:
use List::Util qw/reduce/;
sub factorial {
reduce { $a * $b } 1 .. $_[0];
}
This returns false if the number is <= 1 or a string and a number if a number is passed in (rounding down if a fraction).
And looking forward to Perl 6, it looks like this:
sub factorial {
[*] 1..$^x
}
And also ( from the blog in the link above ) you can even implement this as an operator:
sub postfix:<!>(Int $x) {
[*] 1..($x || 1)
}
and then use it in your code like so:
my $fact5 = 5!;
If you have a comma separated list of flags, and want a lookup table for them, all you have to do is:
my %lookup = map { $_ => 1 } split /,/, $flags;
Now you can simply test for which flags you need like so:
if ( $lookup{FLAG} ) {
print "Ayup, got that flag!";
}
I am surprised no one has mentioned this. It's a masterpiece in my opinion:
#!/usr/bin/perl
$==$';
$;||$.| $|;$_
='*$ ( ^#(%_+&~~;# ~~/.~~
;_);;.);;#) ;~~~~;_,.~~,.* +,./|~
~;_);#-, .;.); ~ ~,./##-__);#-);~~,.*+,.
/|);;;~~#-~~~~;.~~,. /.);;.,./#~~#-;.;#~~#-;;
;;,.*+,./.);;#;./#,./ |~~~~;#-(#-__#-__&$#%^';$__
='`'&'&';$___="````" |"$[`$["|'`%",';$~=("$___$__-$[``$__"|
"$___"| ("$___$__-$[.%")).("'`"|"'$["|"'#").
'/.*?&([^&]*)&.*/$'.++$=.("/``"|"/$[`"|"/#'").(";`/[\\`\\`$__]//`;"
|";$[/[\\$[\\`$__]//`;"|";#/[\\\$\\.$__]//'").'#:=("#-","/.",
"~~",";#",";;",";.",",.",");","()","*+","__","-(","/#",".%","/|",
";_");#:{#:}=$%..$#:;'.('`'|"$["|'#')."/(..)(..)/".("```"|"``$["|
'#("').'(($:{$'.$=.'}<<'.(++$=+$=).')|($:{$'.$=.'}))/'.("```;"|
"``$[;"|"%'#;").("````'$__"|"%$[``"|"%&!,").${$[};`$~$__>&$=`;$_=
'*$(^#(%_+&#-__~~;#~~#-;.;;,.(),./.,./|,.-();;#~~#-);;;,.;_~~#-,./.,
./#,./#~~#-);;;,.(),.;.~~#-,.,.,.;_,./#,.-();;#~~#-,.;_,./|~~#-,.
,.);););#-#-__~~;#~~#-,.,.,.;_);~~~~#-);;;,.(),.*+);;# ~~#-,
./|,.*+,.,.);;;);*+~~#-,.*+,.;;,.;.,./.~~#-,.,.,.;_) ;~~~
~#-,.;;,.;.,./#,./.);*+,.;.,.;;#-__~~;#~~#-,.;;,.* +);;
#);#-,./#,./.);*+~~#-~~.%~~.%~~#-;;__,. /.);;##- __#-
__ ~~;;);/#;#.%;#/.;#-(#-__~~;;;.;_ ;#.%~~~~ ;;()
,.;.,./#,. /#,.;_~~#- ););,.;_ );~~,./ #,.
;;;./#,./| ~~~~;#-(#- __,.,.,. ;_);~~~ ~#
-~~());; #);#-,./#, .*+);;; ~~#-~~
);~~);~~ *+~~#-);-( ~~#-#-_ _~~#-
~~#-);; #,./#,.;., .;.);# -~~#-;
#/.;#-( ~~#-#-__ ~~#-~~ #-);#
-);~~, .*+,./ |);;;~ ~#-~~
;;;.; _~~#-# -__);. %;#-(
#-__# -__~~;# ~~#-;; ;#,.
;_,.. %);#-,./#, .*+,
..%, .;.,./|) ;;;)
;;#~ ~#-,.*+,. ,.~~
#-); *+,.;_);;.~ ~););
~~,.; .~~#-);~~,.;., ./.,.;
;,.*+ ,./|,.); ~~#- );;;,.(
),.*+); ;#~~/|#-
__~~;#~~ $';$;;
I absolutely love Black Perl (link to version rewritten to compile under Perl 5). It compiles, but as far as I can tell it doesn't actually do anything.
That's what you get for a language written by a linguist from a pragmatic perspective rather than from a theoretical perspective.
Moving on from that, you can think about the Perl that people complain about as pidgin Perl (perfectly useful, but not expressive, and beware of trying to express anything complex in it), and the stuff that #pjf is talking about as "proper" Perl, the language of Shakespeare, Hemingway, Hume and so on. [edit: err, though easier to read than Hume and less dated than Shakespeare.] [re-edit and hopefully less alcoholic than Hemingway]
Adding to the love of map and grep, we can write a simple command-line parser.
my %opts = map { $_ => 1 } grep { /^-/ } #ARGV;
If we want, we can set each flag to it's index in #ARGV:
my %opts = map { $ARGV[$_] => $_ } grep { $ARGV[$_] =~ /^-/ } 0 .. $#ARGV;
That way, if a flag has an argument, we can get the argument like this:
if( defined( $opts{-e} ) ) {
my $arg = $ARGV[ $opts{-e} ];
# do -e stuff for $arg
}
Of course, some people will cry that we're reinventing the wheel and we should use getopt or some variant thereof, but honestly, this was a fairly easy wheel to reinvent. Plus, I don't like getopt.
If you don't like how long some of those lines are, you can always use intermediate variables or just convenient line breaks (hey, Python fanatics? You hear that? We can put one line of code across two lines and it still works!) to make it look better:
my %opts = map { $ARGV[$_] => $_ }
grep { $ARGV[$_] =~ /^-/ } 0 .. $#ARGV;
This file parsing mechanism is compact and easy to customize (skip blank lines, skip lines starting with X, etc..).
open(H_CONFIG, "< $file_name") or die("Error opening file: $file_name! ($!)");
while (<H_CONFIG>)
{
chomp; # remove the trailing newline
next if $_ =~ /^\s*$/; # skip lines that are blank
next if $_ =~ /^\s*#/; # skip lines starting with comments
# do something with the line
}
I use this type of construct in diverse build situations - where I need to either pre or post process payload files (S-records, etc..) or C-files or gather directory information for a 'smart build'.
My favourite elegant Perl feature is that it uses different operators for numerical values and string values.
my $string = 1 . 2;
my $number = "1" + "2";
my $unambiguous = 1 . "2";
Compare this to other dynamic languages such as JavaScript, where "+" is used for concatenation and addition.
var string = "1" + "2";
var number = 1 + 2;
var ambiguous = 1 + "2";
Or to dynamic languages such as Python and Ruby that require type coercion between strings and numberical values.
string = "1" + "2"
number = 1 + 2
throws_exception = 1 + "2"
In my opinion Perl gets this so right and the other languages get it so wrong.
Poorer typists like me who get cramps hitting the shift key too often and have an almost irrational fear of using a semicolon started writing our Perl code in python formatted files. :)
e.g.
>>> k = 5
>>> reduce(lambda i,j: i*j, range(1,k+1),1)
120
>>> k = 0
>>> reduce(lambda i,j: i*j, range(1,k+1),1)
1