Passing results of a substitution to a function

[Anonymous Monk]

Hi I'm trying to get a regular expression to pass the results of a regular expression substitution into a method argument. Rather than just make a temporary variable and do the substitution on that, and then pass that to the function, is there any way I can do the substitution as part of the argument list, eg:

$word = 'BLAHBLAH';
print blah(s/BLAH/COW/);
print "$word\n";

sub blah {
my $stuff = shift;
print "$stuff\n";
}

I want to keep the blah method as general as possible, and don't want to add the regular expression there. This is purely a style issue (as I think something like this would look much nicer than having to use one-off variables)

[Pardus]

This can't be done directly since the search and replace functions return the number of matches, not the string.

But you could do this:

$word = 'blah';
print my_sub(map {s/blah/cow/; $_} ($word));

although it _is_ a one-liner it won't get a beauty price either.
--
Jaap Karssenberg || Pardus (Larus)? <[e-mail]>
>>>> Zoidberg: So many memories, so many strange fluids gushing out of patients' bodies.... <<<<

[boo_radley]

Yes, there is a way you can pass a regex -- as a scalar -- around. See qr// in perlop.

[Coruscate]

You could always use grep. Note that I changed the print() in blah() to a return, otherwise you'll end up printing an extra value out.:

my $word = 'BLAHBLAH';
print blah(grep{s/BLAH/COW/}$word);

sub blah {
  my $stuff = shift;
  return "$stuff\n";
}

[Anonymous Monk]

Ok - I now have something which works a lot more niftily:

my $word = 'BLAHBLAH'
blah(grep {s/BLAH/COW/ || 1 } $word);

The { s/BLAH/COW/ || 1 } bit is required as I want to also pass in arguments which do not contain 'BLAH' (which grep would usually.. er.. grep away ;) ). I was worried about list context before because I was trying to get around this by using

blah(grep(s/BLAH/COW/,$word)||$word)

[Anonymous Monk]

This seems to work quite nicely - but needs a small amount of tweaking to make sure grep doesn't return stuff in scalar context.

[BrowserUk]

Your sample code doesn't make much sense in that you are not applying the s/// to anything.

You say you want to pass the results of the s/// to the sub, without recourse to a temporary var. If your intent is to apply the s/// to $word, then this requires no additional vars.

$word = 'BLAHBLAH';
$word =~ s/BLAH/COW/;
print blah( $word );
print "$word\n";

It's not clear to me if this is what you want, but if it's not, maybe you could clarify for me?

---

Examine what is said, not who speaks.

The 7th Rule of perl club is -- pearl clubs are easily damaged. Use a diamond club instead.

[Anonymous Monk]

I want to apply the s/// to $word, but I want to keep the contents of $word as is. It's a one-off non-permanent substitution I'm making (for the purpose of feeding arguments into the method).

[BrowserUk]

You could do this ... whether you should is for your own concience:)

sub blah{print +shift;}

my $word = 'BLAHBLAH';
blah( do{ (local $_= $word) =~ s/BLAH/COW/g; $_} );
# prints COWCOW
print $word;
# prints BLAHBLAH

---

Examine what is said, not who speaks.

The 7th Rule of perl club is -- pearl clubs are easily damaged. Use a diamond club instead.

[jepri]

Intruiging - it works for matches, but not for substitutes.

____________________
Jeremy
I didn't believe in evil until I dated it.