cheat sheets.

* b[reak]
  list breakpoints
* b[reak] [file|class:]LINE|METHOD [if expr]
* b[reak] [class.]LINE|METHOD [if expr]
  set breakpoint to some position, optionally if expr == true
* cat[ch]
  show catchpoint
* cat[ch] EXCEPTION
  set catchpoint to an exception
* disp[lay] EXPRESSION add expression into display expression list
* undisp[lay][ nnn]
  delete one particular or all display expressions if no expression number given
* del[ete][ nnn]
  delete some or all breakpoints (get the number using “break”)
* c[ont]
  run until program ends or hit breakpoint
* r[un]
  alias for cont
* s[tep][ nnn]
  step (into methods) one line or till line nnn
* n[ext][ nnn]
  go over one line or till line nnn
* w[here]
  displays stack
* f[rame]
  alias for where
* l[ist][ (-|nn-mm)]
  list program, - list backwards, nn-mm list given lines. No arguments keeps
  listing
* up[ nn]
  move to higher frame
* down[ nn]
  move to lower frame
* fin[ish]
  return to outer frame
* q[uit]
  exit from debugger
* v[ar] g[lobal]
  show global variables
* v[ar] l[ocal]
  show local variables
* v[ar] i[nstance] OBJECT
  show instance variables of object
* v[ar] c[onst] OBJECT
  show constants of object
* m[ethod] i[nstance] OBJECT
  show methods of object
* m[ethod] CLASS|MODULE
  show instance methods of class or module
* th[read] l[ist]
  list all threads
* th[read] c[ur[rent]]
  show current thread
* th[read] [sw[itch]] nnn
  switch thread context to nnn
* th[read] stop nnn
  stop thread nnn
* th[read] resume nnn
  resume thread nnn
* p EXPRESSION
  evaluate expression and print its value
* pp EXPRESSSION
  evaluate expression and print its value
* h[elp]
  print this help
* RETURN KEY
  redo previous command. Convenient when using list, step, next, up, down,
* EVERYHTING ELSE
  evaluate