Perl - Instructor Insights

Our instructors have real-world experience in the technologies that they teach. Here they share their insights and discoveries on working with each of these technologies.

Perl can be used to convert UNIX text files to Windows text files.

Use this perl one-line program to convert Windows to UNIX text files:

	perl -pi -e 's/\r\n/\n/g' dosfile.txt

Use a similar program to convert UNIX to Windows text files:

	perl -pi -e 's/\n/\r\n/' unixfile.txt

Use parentheses to indicate precedence, rather than memorizing the precedence rules.

This is especially important in Perl, as the precedence rules can be tricky:

	print  (1 + 2) * 3, "\n";

will not compute (1 + 2) * 3, then print the resulting 9 on a line by itself. Instead, the (1 + 2) will be assumed to indicate a function call bound to "print". The remaining "* 3" and newline will processed, but will result in no actions and the results will be ignored.

Lists are not the same as arrays.

While lists and arrays are often used interchangeably when talking about Perl, they are not the same. Examples: an array processed in scalar context will return the number of items in the array, while a list in scalar context will return the last item in the list; arrays have changeable length, while lists have a fixed length; variables can be array types, using the '@' character — they cannot be lists.