> On 13 Mar 2017, at 22:20, ToddAndMargo <toddandma...@zoho.com> wrote: > > On 03/13/2017 02:11 PM, Elizabeth Mattijsen wrote: >> >>> On 13 Mar 2017, at 22:06, ToddAndMargo <toddandma...@zoho.com> wrote: >>> >>> Hi All, >>> >>> $ perl6 -e 'my $x="ab12cd"; $x ~~ m/ab(1q2)cd/; say "$x\n\$0=<$0>\n";' >>> Use of Nil in string context in block <unit> at -e line 1 >>> ab12cd >>> $0=<> >>> >>> With out the "q" in this, it works. I deliberately put >>> the "q" to see what would happen when a patter was not >>> found. >>> >>> Is there a way around the "use of nil" finger wag >>> if a patter is not found? >> >> The Nil is not caused by the smart match, but from your attempt to display >> the first positional capture (aka $0) of a match that failed. >> >> >>> Or should I always test for its presence first if >>> there is a possibility the pattern might not exist? >> >> You should test whether the smart match was successful. >> >> my $x="ab12cd"; say "$x\n\$0=<$0>\n” if $x ~~ m/ab(1q2)cd/; >> >> >> >> Liz >> > > Hi Liz, > > Thank you! > > How would you do this if there were several matches in the line? > > if $x ~~ m/(ab)(1q2)(cd)/; > > Eventually break down an use .defined?
This is about the entire smart match, the result of the ~~ operator. Either it returns true, and then everything is set in $/ (and it’s derived fields like $<foo> if you’re using named captures). Or it returns false, and then nothing is set, it’s all Nil. HTH, Liz
