Just in time processing on a character stream

Just in time processing on a character stream is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Given a stream of characters, presumably (simulated) from a keyboard, that contain the separators "formfeed", "linefeed", "tab" and "space" characters. Print out the i^th character of the i^th tab-field of the i^th line of the i^th page to reveal a secret password.

Stop processing immediately upon encountering a "!" found uniquely in this i,i,i,i position (least the system self destruct). The "!" may be found/permitted else where however, in which case it should be ignored.

Ideally this can be generalise as follows:

• The separators (formfeed, linefeed, tab, space) provided from a user supplied array and can include additional/alternative separators, e.g. (formfeed, linefeed, ".", "," ," ",...).
• These selection criterial is generalised i^th,i^th,i^th,i^th to a boolean function of f(page,line,field,word,...) or f(i^th,j^th,k^th,l^th,m^th,etc...)

Provide a reasonably interesting message to be decoded, e.g. Silence-Dogood. Your choice.

This task was inspired by the movie "National Treasure" with refers to a "book cipher".