perl6 grep like program in parallel

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I wrote a grep-like program in perl6, and now I made it into parallel processing. But I ran into some problem: even with the same command line the program sometimes succeeds, and sometimes fails. When it succeeds, things looks just normal to me. When it fails, I don't know why...

Here is the error message when it fails.

> grep6 perl * An operation first awaited: in sub MAIN at /Users/xxx/Dropbox/bin/grep6 line 28 in block <unit> at /Users/xxx/Dropbox/bin/grep6 line 30  Died with the exception: Cannot find method 'Any' on object of type Match   in regex  at /Users/xxx/Dropbox/bin/grep6 line 34   in sub do_something at /Users/xxx/Dropbox/bin/grep6 line 34   in block  at /Users/xxx/Dropbox/bin/grep6 line 24 

And the code is:

#!/usr/bin/env perl6    constant $color_red = "/e[31m"; constant $color_off = "/e[0m";  sub MAIN(Str $pattern, *@filenames){     my $channel =;     $channel.send($_) for @filenames; # dir();     $channel.close;     my @workers;     for 1..3 -> $n {         push @workers, start {             while (my $file = $channel.poll) {                 do_something($pattern, $file);             }         }      }     await(@workers); }  sub do_something(Str $pattern, Str $filename) {     #say $filename;     for $filename.IO.lines -> $line  {         my Str $temp = $line;         if $temp ~~ s:g/ (<$pattern>) /$color_red$0$color_off/ {              say $filename ~ ": " ~ $temp;         }     } } 

My question is why it fails sometimes?




Did a bit of playing about the issue seems to be the anonymous regexp you're creating by doing :

s:g/ (<$pattern>) /$color_red$0$color_off/ 

If you instead precompile your regex (either in do_something or the MAIN routine then the errors stop. Here's the updated do_something version :

sub do_something(Str $pattern, Str $filename) {     my $reg = regex { $pattern };     for $filename.IO.lines -> $line  {         my Str $temp = $line;         if $temp ~~ s:g/ ($reg) /$color_red$0$color_off/ {              say $filename ~ ": " ~ $temp;         }     } } 


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