LSE, Language Sensitive Editor, a text editing tool used most commonly by programmers for the purpose of software development.
Found on Open-VMS (VMS) systems, LSE includes such features as:

• An interface that is completely keyboard driven.
• Compiling in the editor.
• Searching text for presence of characters or patterns.
• Substituting character strings or character string patterns.
• Defining keys in the editor to simplify repetitious tasks.