How to reorder a text file

hennesse has asked for the wisdom of the Perl Monks concerning the following question:

I have a 15,000 line text file where I want to "reverse" groups of lines. In the example below, a group is a Title followed by 0 or more lines of text. What is an efficient approach to do this?

Input file:

Title 1
Line of text A
Line of text B
Title 2
Line of text C
Title 3
Title 4
Line of text D
[download]

Desired Output:

Title 4
Line of text D
Title 3
Line of text D
Title 3
Title 2
Line of text C
Title 1
Line of text A
Line of text B
[download]

Thanks, Dave

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