perl6有色匹配,一些正则表达式插值有效,有些则没有;颜色代码不一

sub colorMatch ($aStr,$aRegex,$aColor) {
    my $colorOff = 'e[0m';
    my $a =$aStr.subst(/(<{$aRegex}>)/,$aColor ~ "# $/ #" ~ $colorOff,:g);
    # not working,$/ not interpolating corresponding matches,all Nil
    say $a;
}

colorMatch("a-12-b-3-c-4-def-567",'d+','e[1;31m');
colorMatch("a-12-b-3-c-4-def-567",'<alpha>+','e[1;31m');
say "e[1;31m" ~ " color1 " ~ "e[0m" ~ 
    "e[1;36m" ~ " color2 " ~ "e[0m";

sub colorMatch2 ($aStr,$colorNumber) {
    my $colorOff = "e[0m";
    if $aStr.chars > 0 {
    my $x1 = ($aStr ~~ m/<{$aRegex}>/);
    my $x2 = $x1.prematch;
    my $x3 = $x1.Str;
    my $x4 = $x1.postmatch;
    return ($x2 ~ "e[1;{$colorNumber}m" ~ $x3 ~ $colorOff)
        ~ colorMatch2($x4,$colorNumber);
    }
}

say colorMatch2("a-12-b-3-c-4-def-567",31); # works,red color
say colorMatch2("a-12-b-3-c-4-def-567",'567',36); # works,green color
say colorMatch2("a-12-b-3-c-4-def-567",'w+','[a..z]+',31); # fails with [] and ..
say colorMatch2("a-12-b-3-c-4-def-567","<alpha>+",31); # fails with <>


Use of Nil in string context
  in sub colorMatch at colorMatch.pl line 4
a-e[1;31m#  #e[0m-b-e[1;31m#  #e[0m-c-e[1;31m#  #e[0m-def-e[1;31m#  #e[0m

# seems to do substitution,but $/ is empty and color not shown;

Use of Nil in string context
  in sub colorMatch at colorMatch.pl line 4
e[1;31m#  #e[0m-12-e[1;31m#  #e[0m-3-e[1;31m#  #e[0m-4-e[1;31m#  #e[0m-567

# seems to do substitution,but $/ is empty and color not shown;

 color1  color2 # both colors work and shown as expected,# color1 red and color 2 green; why inconsistent with above???

a-12-b-3-c-4-def-567 # works,red color
a-12-b-3-c-4-def-567 # works,green color
a-12-b-3-c-4-def-567 # works,red color
No such method 'prematch' for invocant of type 'Bool'
  in sub colorMatch2 at colorMatch.pl line 17
  in block <unit> at colorMatch.pl line 28