quick question about parenthesis and regular expressions

[cranberry13]

Hello there!

I have a quick question about using regular expresssions.

I want to match

 $word =~ /absorb|absorbs|absorbed/i

and save the match in $1 (and supposing there can only be one match), how do I place the 'parenthesis'?

This doesn't work:

 $word =~ /(absorb|absorbs|absorbed)/i

What am I doing wrong?

[Enlil]

But it DOES work. If $word contains "absorb" in it at all $1 will be set to absorb, after the match.

One thing of note is that $1 will never match absorbs nor absorbed, as as it will match absorb first, the regex engine will consider the regex a success and stop. if on the other hand you want to match absorbed or absorbs you might want to change the order of the alternation around, so that the last thing it attempts to match is absorb. or for less backtracking you might try something like:

$word =~ /(absorb(?:s|ed)?)/i; print $1;

updated:added the ? as per ysth below. ysth++ for catching my oversight.

-enlil

[ysth]

You need to say (?:s|ed)? or "absorb" won't match.

[cranberry13]

Enlil--
Thanks for the reg expression -- it works :)

But here's an interesting problem, it seems if i'm using a regular expression with the substitution operator, the value of $1 comes up blank.

Why is that?

What I really want to do is this:

if ($line =~ s/($word(?:s|ed))/<b>$1<\/b>/igm)

assuming that:

$line= "She was very absorbed in her homework.";
$word = "absorb";

I want it to match absorbed and but store the value of it in $1 so that I can use it later.

[jreades]

Ummm, I have no problem doing the substitution using the code supplied:

$line = "She was very absorbed in her homework.";
$word = "absorb";

print STDOUT "Line: $line\n";
$line =~ s/($word(?:s|ed))/<b>$1<\/b>/igm;
print STDOUT "New Line: $line\n";
print STDOUT "\$1 contains: $1\n";

Of course, I might consider changing it slightly to read:

$line =~ s/\b(${word}(?:s|ed)?)\b/<b>$1<\/b>/igm;

However, I did just discover that there is something more going on here, because while the original (without the \b) does set something in $1, my change doesn't (despite doing the substitution properly).

And finally, if you're just doing a match why are you using s///?

[PodMaster]

Define "work" because according to my definition, it does ;)

for my $word ( qw[ absorb absorbo absorbs absorbed absorbarararara ]){
    $word =~ /(absorb|absorbs|absorbed)/i
    and warn " $1 ";
}
__END__
 absorb  at - line 2.
 absorb  at - line 2.
 absorb  at - line 2.
 absorb  at - line 2.
 absorb  at - line 2.

Perhaps you wish to investigate some anchors (namely ^ and $). Also of interest might be (besides the manual pages) YAPE::Regex::Explain.

update: Enlils response reminded me of Regex::PreSuf

use Regex::PreSuf;
my $re = presuf(qw(absorb absorbs absorbed absorbing ));
die $re;
__END__
absorb(?:ed|ing|s)? at - line 3.