Tips

Remove AnsiEscaped colors
- perl -pe 's/\e\[[0-9;]*m(?:\e\[K)?//g' # Adam Katz's trick
use Number::Format ‘format_number’
glob
.perldlrc # to edit and load automatically some libs
Use Unicode::Collate::Sort

Symbol table edition

for (keys %main::){say}
*sym = $main::{"/"}

Interpolate code in string = @{[LIST EXPR]} or ${\(SCALAR EXPR)}
- say "@{[ 3 + 4 ]}"
- say "${\ function }" -> say "${\ do { 3 + 4 }}" or say "${\( 3 + 4 )}"
- Use dot operator
- print <<"EOT"; This is $x EOT : interpolates
- print <<'EOT'; This is $x EOT : do NOT interpolate

my $foo = "zombies are the bombies";if ($foo =~ / zombie # sorry pirates /x ) { print “urg. brains.”;} /x modifier for pretty regzx print

Even without the /x modifier, you can enclose comments in (? # … ):my $foo = “zombies are the bombies”;if ( $foo =~ /zombie(?# sorry pirates)/ ) { print “urg. brains.”;}

Add to path use lib qw(.); # Will add your cwd to @INC use lib qw(. /path/to/my/home /some/other/dir); # will add those dirs perl -I/path/to/include script

Get package path perl -MTime::HiRes -e ‘print $INC{“Time/HiRes.pm”}’ or perldoc -l Time::HiRes cpan -D Time::HiRes

How do I completely remove an element from an array?

@array = grep { $_ != $element_omitted } @array;
```
@files = qw(/foo/bar/file.pdf /foo/baz/file2.jpg);

foreach $file (@files) {

exclude any files whose full name contains the string ‘bar’

        next if $file =~ /bar/;

print all other files

        print "$file\n";
}
```

Pdl

pdl >demo

Profiling

perl -d:DProf program.pl
dprofpp
dprofpp -p program.pl
perl -d:NYTProf some_perl.pl
nytprofhtml

perldoc perldebguts

Print Hash

print "$_ $h{$_}\n" for (keys %h);

Extend @LIB

export PERL5LIB=/home/foobar/code
use lib '/home/foobar/code';
use My::Module;
perl -I /home/foobar/code script.pl

That is a capital i like include

Fork Bomb

perl -e "fork while fork" &

Console

perl -de1

debugging a trivial programe

Write multiple line regex
* Delete the space, then type CtrlV, CtrlJ.
Then Return.
The Ctrl-V prevents the shell interpreting the next character (newline) literally. * toto

Match brace, bracket or parenthesis * Use Text::Balanced * my $re; $re = qr/ \{ (?: [^{}]* | (??{$re}) )* \} /x; my @array = $str =~ /$re/xg;

Get environment variables * $userName = $ENV{'LOGNAME'}; * print “Hello, $userName”;

Installing modules

tar zxf Digest-SHA1-2.13.tar.gz cd Digest-SHA1-2.13 perl Makefile.PL make make test make install

tar zxf … cd … perl Build.PL ./Build ./Build test ./Build install

Command line

Interactive shell * perl -de1 * rlwrap perl -d -e 1 * perlconsole (get history) * see psh * reply (the best because it uses readline)

Change file content * perl -i.bak -p -e ‘s/old/new/g;’ *.config

Argument	Description
-0	Split on NULL byte (almost never)
-00	Split on paragraph
-0777	Treat the file as a whole (do not delete new lines)
-I path	Add path to @INC
-i[.bak]	Do in place substitution like :
	`perl -i.bak -ne 'print unless /^ #/' script.sh`
-a	Enable autosplit mode : split input lines on whitespace into the @F array
	`ls -l <bar> perl -lane 'print "$F[7] $F[1]"'`
-F:	Choose the -a delimiter (here :)
	`perl -F: -lane 'print $F[0]' /etc/passwd`

-MModule	Include module : `-MRegexp::Common`
	`perl -MList::Util=max -ape 's/$/" " . max(@F)/e unless $.==1' input`
	`-Mmodule=foo,bar` is `use module split(/,/,q{foo,bar})`
-n	Process files line by line
-p	Process line by line and print output
-l	Remove newline char before giving line to you (and add it at the end)
-v	Check Perl version

The perl command is in apostrophes, and escaping those is hard work… So if your regex happens to contain apostrophes, first place it in an env variable then refer to it by name :

env mypattern="'\w+" perl -0777 -ne 'while(m/$ENV{mypattern}/g){print "$&\n";}' yourfile

Packages

cpan install CPAN cpan reload cpan

Cwd	Change working directory
Reply	Read Execute Print Loop
PDL	Perl Data Library
PDL::IO::Image	Image manipulation (object)

Regexp

Regexp	Meaning
`(?=regex)`	Positive lookahead
`(?!regex)`	Negative lookahead
`(?=(regex))`	Capturing lookahead
`(?<=text)b`	Positive lookbehind
`(?<!text)b`	Negative lookbehind
`(?:regex)`	Non capturing group
`\K`	in vim (start recording)

Modifer	Meaning
s	Include newlines in .
m	Include newlines in ^ and $
r	Non destructive
x	Pretty print regex: ignore space, newline, comment
e	Execute replacement expression