Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Problem: $pyrich just saves only one letter not the whole hit.   Why?

Code: my($branch, $pyrich) = /(ct(a|g)a(c|t))(.{20,50})$/i;

$branch is ok
whole hit is ok
But $pyrich prints just one single letter although whole hit is ok so it must be 20-50 letters long.   Where is my fault?

janitored by ybiC: Minor format cleanup, including balanced <code> tags around snippet.

Replies are listed 'Best First'.
Re: Regex: save values
by mrborisguy (Hermit) on Jun 12, 2005 at 18:16 UTC

    It looks to me (and somebody can correct me if I'm wrong), that $branch will contain whatever was found in (ct(a|g)a(c|t)), but then $pyrich will find what was found in (a|g). I think your FOURTH save would be the 20 to 50 character save.

        -Bryan

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Re: Regex: save values
by davidrw (Prior) on Jun 12, 2005 at 19:24 UTC
    As already mentioned, it's related to the capture orders. You can use ?: to just do clustering and not capturing to make it easier/clearer (see perldoc perlre): 
    if ( /(ct(?:a|g)a(?:c|t))(.{20,50})$/i ){
  $branch = $1;  # this will be 'ctXaX'
  $pyrich = $2;  # this will be the 20-50 chars at the end
}

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[d/l]
[select]
      Oh dear... you all are so right. It was intended to be
      /(ct(?:a|g)a(?:c|t))(.{20,50})$/i
      of course... you sometimes need the help of others to see clear... LOL
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Re: Regex: save values
by dReKurCe (Scribe) on Jun 12, 2005 at 18:44 UTC

    Picking apart your regex by using the following code reveals that the the final block of characters is contained in $4. This is the problem. You were mistakingly assigning $2, witch is matched inside the first group,as this code shows. 
    $string="ctaacxxxxxxxxxxxxxxxxxxxxxxx";
$_=$string;
$_=/(ct(a|g)a(c|t))(.{20,50})$/i;
print "\n$1,$2,$3,$4";
($branch,$pyrich)=($1,$4);
print "\n$branch$pyrich";

    [download]
    produces: 
    ctaac,a,c,xxxxxxxxxxxxxxxxxxxxxxx
ctaacxxxxxxxxxxxxxxxxxxxxxxx

    [download]

    Hope that helps.
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[d/l]
[select]
      This might also be a good place to use the extended (/x) regex syntax, with whitespace and comments, and strategic indenting, to better understand what's going on. 
      use strict;
use warnings;

"ctaacxxxxxxxxxxxxxxxxxxxxxxx" =~ 
/
( #begin $1
    ct
    (a|g) # $2
    a
    (c|t) # $3
) #end $1
(.{20,50})$ # $4
/ix;

print "\n$1,$2,$3,$4";
my ($branch,$pyrich)=($1,$4);
print "\n$branch$pyrich";

      [download]
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[d/l]
Re: Regex: save values
by Anonymous Monk on Jun 12, 2005 at 18:01 UTC
    I saved it now in an array not in a scalar and joined the fields... Now everything works fine.
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