Well in my opinion for readability its such a small tradeoff that really its not worth not putting it in 2 vars first.

Just to make Sunny look like a good guy:

alias randtok { tokenize -i $2 $1 | return $($ $+ $r(1,$0),2) }

You're missing an 'i' in tokenize, @SReject

well you right @Sorasyn but it easier to read in the old way, but you 100% right :)
@SReject your code is use less 3 bytes less then @Sorasyn one :)

@Conscious Fixed

@thegingon I had a typo. Its fixed now, And I did it just to show that Sunny's wasn't the worst 'shortcode' for readability

Eh I couldnt make it shorter but I could make it even more less readable :)

alias randtok { return $regsubex($1,/(.+?)(?:\x $+ $base($2,10,16) $+ |$)/g,) $+ $regml($r(1,$regml(0))) }

Well @[Plornt], you did it :)

Well @[Plornt], I made yours shorter

alias randtok return $regsubex($1,/(.+?)(?:\x $+ $base($2,10,16) $+ |$)/g,) $+ $regml($r(1,$regml(0)))

Not to be that guy but.... @[Plornt] & Savage_CL:

alias randtok return $regml($r(1,$regex($1,/([^\x $+ $base($2,10,16) $+ ]+)/g)))

Slightly shorter than yours, @SReject :

alias randtok return $regml($r(1,$regex($1,/([^\ $+ $base($2,10,8) $+ ]+)/g)))

Unfortunately, I'm not adept enough with mIRC to be a contender in this war of bytes.