The Jargon File (version 4.4.7, 29 Dec 2003):

proglet
 /prog'let/, n.

    [UK] A short extempore program written to meet an immediate, transient
    need. Often written in BASIC, rarely more than a dozen lines long, and
    containing no subroutines. The largest amount of code that can be written
    off the top of one's head, that does not need any editing, and that runs
    correctly the first time (this amount varies significantly according to
    one's skill and the language one is using). Compare toy program, noddy,
    one-liner wars.


The Free On-line Dictionary of Computing (30 December 2018):

proglet

   /prog'let/ [UK] A short extempore program written to meet an
   immediate, transient need.  Often written in BASIC, rarely
   more than a dozen lines long and containing no subroutines.
   The largest amount of code that can be written off the top of
   one's head, that does not need any editing, and that runs
   correctly the first time (this amount varies significantly
   according to one's skill and the language one is using).
   Compare toy program, noddy, one-liner wars.

   [Jargon File]