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?

Many thanks,
-T


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