Abbreviations simple

Demonstrate that inputting an empty string returns an empty string in addition to the required test input.

<
add 1  alter 3  backup 2  bottom 1  Cappend 2  change 1  Schange  Cinsert 2  Clast 3
compress 4 copy 2 count 3 Coverlay 3 cursor 3  delete 3 Cdelete 2  down 1  duplicate
3 xEdit 1 expand 3 extract 3  find 1 Nfind 2 Nfindup 6 NfUP 3 Cfind 2 findUP 3 fUP 2
forward 2  get  help 1 hexType 4  input 1 powerInput 3  join 1 split 2 spltJOIN load
locate 1 Clocate 2 lowerCase 3 upperCase 3 Lprefix 2  macro  merge 2 modify 3 move 2
msg  next 1 overlay 1 parse preserve 4 purge 3 put putD query 1 quit  read recover 3
refresh renum 3 repeat 3 replace 1 Creplace 2 reset 3 restore 4 rgtLEFT right 2 left
2  save  set  shift 2  si  sort  sos  stack 3 status 4 top  transfer 3  type 1  up 1
> ~~ m:g/ (<.alpha>+) \s* (\d*) /;

my %abr = '' => '', |$/.map: {
    my $abbrv = .[0].Str.fc;
    |map { $abbrv.substr( 0, $_ ) => $abbrv.uc },
    +(.[1].Str || .[0].Str.chars) .. .[0].Str.chars;
};

sub abbr-simple ( $str ) { %abr{$str.trim.fc} // '*error*' }

# Testing
for 'riG   rePEAT copies  put mo   rest    types   fup.    6       poweRin', '' -> $str {
    put ' Input: ', $str;
    put 'Output: ', join ' ', $str.words.map: &abbr-simple;
}

Output:

 Input: riG   rePEAT copies  put mo   rest    types   fup.    6       poweRin
Output: RIGHT REPEAT *error* PUT MOVE RESTORE *error* *error* *error* POWERINPUT
 Input: 
Output: