Perl tips - array of records, command line params, STDIN/STDOUT handles

set of records or 2D array

• To store a set of records, use  my @data; $data[i]->[j] = $someval; (ith record, jth field). This basically works similar to a 2-D array except that each row can have different size.
• To sort the records based on column j, do @sorteddata = sort {$a->[j] <=> $b->[j]} @data;.

Command line parameters

• The format for specifying parameters is cmd OPT1=sth OPT2=sth ...
• Use while(@ARGV){ if(m{OPT1=}){ use $'; }elsif(m{OPT2}){...}}.
  

Others

• Use $opstream = *STDOUT; (note the '*') to pass (both read and write) file handles around and use them via variables (e.g. print $opstream "qwe";).
• To get floor of a number, do use POSIX; $val = POSIX::floor($num);.