Question

I need to pass a regex substitution as a variable:

sub proc {     my $pattern = shift;     my $txt = "foo baz";      $txt =~ $pattern; }  my $pattern = 's/foo/bar/'; proc($pattern); 

This, of course, doesn’t work. I tried eval’ing the substitution:

eval("$txt =~ $pattern;"); 

but that didn’t work either. What horribly obvious thing am I missing here?

Answer 1

I need to pass a regex substitution as a variable

Do you? Why not pass a code reference? Example:

sub modify {   my($text, $code) = @_;   $code->($text);   return $text; }  my $new_text = modify('foo baz', sub { $_[0] =~ s/foo/bar/ }); 

In general, when you want to pass ‘something that does something’ to a subroutine (‘a regex substitution’ in the case of your question) the answer is to pass a reference to a piece of code. Higher Order Perl is a good book on the topic.