** Using WeBWorK **

I hunted down the source of some unexpected output while developing a problem as the delimiter in regular expressions.  Below are two minimal working examples in pg and perl respectively with the lines identified parenthetically,

     $n=~'\d'  (single quotes)

versus,

      $n=~/\d/  (slash)

as the salient portions.  The single quote method works as I expected in pg but the slash does not.  In perl both characters work identically in the expected manner.  Naively, it appears that the single quote should be used for all such regex cases in pg going forward, but I would appreciate further insight.

----------------------------------------------------------------------------------------------------------------

PG output

Slash delimiter value: 11
Quote delimiter value: 10

----------------------------------------------------------------------------------------------------------------

Perl output

Slash delimiter value: 10
Quote delimiter value: 10

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PG code

DOCUMENT();
loadMacros("PGstandard.pl" );

$input=123.45;

BEGIN_TEXT
Slash delimiter value: \{slash($input)\}$BR
Quote delimiter value: \{quote($input)\}$BR
END_TEXT

sub quote {
  my($n)  = @_;
  if( $n=~'\d'){return 10;}
  else{return 11;}
}

sub slash {
  my($n)  = @_;
  if( $n=~/\d/){return 10;}
  else{return 11;}
}

ENDDOCUMENT();

----------------------------------------------------------------------------------------------------------------

Perl code

$input=123.45;
$ret1=slash($input);
$ret2=quote($input);
print "Slash delimiter value: $ret1\n";
print "Quote delimiter value: $ret2\n";

sub quote {
  my($n)  = @_;
  if( $n=~'\d'){return 10;}
  else{return 11;}
}

sub slash {
  my($n)  = @_;
  if( $n=~/\d/){return 10;}
  else{return 11;}
}