Display - for a program or runtime environment (whatever suits the style of your language) - the top ten most frequently occurring functions (or also identifiers or tokens, if preferred).

This is a static analysis: The question is not how often each function is
actually executed at runtime, but how often it is used by the programmer.

Besides its practical usefulness, the intent of this task is to show how to do self-inspection within the language.

source: to :block read arg\0
frequencies: #[]
 
inspectBlock: function [blk][
    loop blk 'item [
        case []
            when? [word? item][
                sItem: to :string item
                if set? sItem ->
                    if function? var sItem [
                        if? key? frequencies sItem ->
                            set frequencies sItem (get frequencies sItem)+1
                        else ->
                            set frequencies sItem 1
                    ]
            ]
 
            when? [or? block? item
                       inline? item] ->
                inspectBlock item
 
            else []
    ]
]
 
inspectBlock source
 
inspect frequencies