Thanks choroba,

I didn’t know that! This special case must have been implemented for a reason, but I can’t think what it could have been.

Using a non-capturing group to avoid this behaviour is a useful workaround.

The good news is that this special case doesn’t seem to be present in Raku:

23:48 >perl -wE "my $s = ''; say 'match1' if 'abc' =~ /b/; say 'match2
+' if 'adc =~ /(?:$s)/;"
match1
match2

23:55 >perl -wE "my $s = ''; say 'match1' if 'abc' =~ /b/; say 'match2
+' if 'adc =~ /$s/;"
match1

23:56 >raku -e "my Str $s = ''; say 'match1' if 'abc' ~~ /b/; say 'mat
+ch2' if 'adc' ~~ /$s/;"
match1
match2

23:56 >
[download]

Cheers,