Top 5 things for perl newbies to do/learn
1. Use strict. Always. It forces certain proper behaviours on you and finds most common errors at compile time.
#!/usr/bin/perl
use strict;
my $foo; # predeclare the scalar
$fpp = "test" # $fpp undefined because you can't type properly, this won't pass perl -c
2. Learn to use the data structures properly. Especially hashes. But especially refs
my $ref; # placeholder
$ref->{foo} = "bar"; # hashref
$ref->{foo}->[0] ="bar"; # now a hashref pointing at an arrayref
3. Data::Dumper - makes sense of fished up structures like the above
$ cat /tmp/test.pl
#!/usr/bin/perl
use strict;
use Data::Dumper;
my $foo;
$foo->{bar}->[0] = "baz";
print Dumper $foo;
$ perl /tmp/test.pl
$VAR1 = {
'bar' => [
'baz'
]
};
3. Learn to use the perl debugger. Putting prints in your code gets real old, real fast
perl -d foo.pl
4. Think about your code because it's really easy to make perl code that sucks... Devel::Profile is a good module to see which functions get called the most and how much time they take. Avoid making the same regex over and over -- save your variables or the results of expensive calculations in a structure.
$foo =~ /^(\d+)/;
my $firstnumbers = $1; # whatever was in parens
($firstnumbers) = ($foo =~ /^(\d+)/); # one line format, a regex returns an array of ($1, $2, ...)
In the last one don't forget to put $firstnumbers in parens because it casts it to an array (in scalar context $~ returns the number of matches, not the values)
Similarly, try to anchor your regexps (^ $) to improve efficiency. Avoid .*, especially multiple .*'s in the same regexp because it probably won't behave the way you think it will
.*? is a non-greedy version, google "perl backtracking" to find more
5. Learn about the perl one liners, especially -p/-n and -i.
perl -p -i.bak -e 's/fish/fsck/g' *.php
will replace fish with fsck in all of the .php files, saving the old file with a .bak extension
