I'd like to pass the result of a regex into a function, as the first of three parameters. For example:

my $str = 'abc';
PassRegex($str =~ /b/i, 'parm2', 'parm3');

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The subroutine looks like this:

use Data::Dumper;
sub PassRegex {
  print Dumper(\@_);
  print "BoolExpr = $_[0]\n";
  print "parm2    = $_[1]\n";
  print "parm3    = $_[2]\n";
  return;
}

[download]

This works fine when the regex evaluates to true (1); if I look at @_ inside the function, I see 1 as the 0th element. However, if I change the regex to /x/i, so that it evaluates to false (the empty string), then the 0th element of @_ seems to disappear. Data:Dumper shows a 0th element, but it is empty -- completely empty, not the empty string -- and $_[0] returns the second parameter. Contrast this case to the case where I explicitly pass in the empty string to the function, and @_ contains what one would expect.

My question is, what do regexes that don't produce a match actually return, if not the empty string? Also, I realize that there are probably other ways to accomplish what I'm trying to do -- for example, I could quote the regex so that it would be evaluated inside the function -- but I'm curious about why this way doesn't work.

In reply to Passing regex result into function by sdsommer

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