Often, I need to compare two variables but I don’t know if they are numbers or strings. I need to know the type so I can pick the proper comparison operators, i.e., == or eq, > or gt.
So, here’s how to do it:

~$x ne ~"$x" ? 'numeric' : 'string'

~ is the bitwise negation operator (see perlop). It does not negate integers and strings in the same way.

Examples:

$ perl -e 'print ~1, "n"'
4294967294
$ perl -e 'print ~"1", "n"'
Œ

(character which ASCII code is 255 – ord(‘1’))

To create a directory path programatically:

use File::Path;

mkpath "/usr/local/apache/htdocs/articles/2003";

This will create the 2003 directory and all parent directories as needed. This is the same as mkdir -p command.

Several times I needed a timestamp for whatever reason. Here’s one that will return a scalar containing the current timestamp as in 03Jun19-114251.

sub create_timestamp {
    my ($sec, $min, $hour, $mday, $mon, $year) = localtime;
    my $month = (qw(Jan Feb Mar Apr May Jun
                    Jul Aug Sep Oct Nov Dec))[$mon];
    $year %= 100;

    my $timestamp = sprintf("%02d%s%02d-%02d%02d%02d",
                         $year, $month, $mday, $hour, $min, $sec);

    return $timestamp;
}

This pair of routines will serialize and deserialize any Perl data. Useful when you have a piece of data that you want to pass accross 2 CGI applications since CGI don’t have persistent state.

sub _serialize {
   my ($self, $data) = @_;

   my $filename = "/tmp/TTS_$$.dat";

   sysopen(OUTFILE, $filename, O_RDWR|O_CREAT, 0666)
     or die ("Can't open $filename: $!");

   flock(OUTFILE, LOCK_EX)
     or die ("Can't lock $filename: $!");

   store($data, $filename)
     or die ("Can't store data structure: $!");

   flock( OUTFILE, LOCK_UN )
     or die ("Can't unlock $filename: $!");

   return $filename;
}

sub _deserialize {
   my ($self, $filename) = @_;

   sysopen(OUTFILE, $filename, O_RDWR|O_CREAT, 0666)
     or die ("Can't open $filename: $!");

   flock(OUTFILE, LOCK_EX)
     or die ("Can't lock $filename: $!");

   my $data = retrieve($filename)
     or die ("Can't retrieve $filename: $!");

   flock( OUTFILE, LOCK_UN )
     or die ("Can't unlock $filename: $!");

   return $data;
}