in reply to Illegal division by zero

One problem: 

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my $x = 'CA006139520,\"WINDSOR RIVERSIDE, ON CA\",2018-01-02,10';
 ;;
 my @windsordigits;
 @windsordigits = $x =~ /WINDSOR\sRIVERSIDE.*(\d\d?)/;
 dd \@windsordigits;
"
[0]

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When the last two digits of the line are '10', why is only '0' captured? The  .* "consumes" as much as possible of non-newline stuff (including digits), the  \d is required for a match, but the  \d? is not, so only one digit is captured. Try something like: 
c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my $x = 'CA006139520,\"WINDSOR RIVERSIDE, ON CA\",2018-01-02,10';
 ;;
 my @windsordigits;
 @windsordigits = $x =~ /WINDSOR\sRIVERSIDE.*\b(\d+)\z/;
 dd \@windsordigits;
"
[10]

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to get all digits at the end of the line. (Update: If the line may end in an un-chomp-ed newline, use  \Z (big-Z) instead of  \z (little-z) as the end-of-line anchor.)

Another problem: 

@windsordigits = ...;

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You're assigning a single item to the array on each pass through the while-loop; the array will never have more than a single item in it no matter how many lines you read. Try something like (untested): 
push @windsordigits, $x =~ /WINDSOR\sRIVERSIDE.*\b(\d+)\z/;

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(Update: E.g.: 
c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my @windsordigits;
 ;;
 for my $x (
     'CA006139520,\"WINDSOR RIVERSIDE, ON CA\",2018-01-02,10',
   qq{CA006139520,\"WINDSOR RIVERSIDE, ON CA\",2018-01-02,987\n},
   qq{CA006139520,\"WINDSOR RIVERSIDE, ON CA\",2018-01-02,6\n},
   ) {
   push @windsordigits, $x =~ /WINDSOR\sRIVERSIDE.*\b(\d+)\Z/;
   }
 dd \@windsordigits;
"
[10, 987, 6]

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Note use of  \Z anchor.)

See the flip-flop operator  .. in perlop for help with the line-range problem. (Update: See use of range operator  .. "As a scalar operator ..." in perlop.)

Give a man a fish:  <%-{-{-{-<

In Section Seekers of Perl Wisdom