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

Hi all,

How would I go about reporting the position in a string of nested matches to a pattern like this 

[XYZ]{3}[A-Za-z]{0,21}[ABC]{3}

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Example: 
FGTXYZGTFABCGHABC

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would result with 3,3

or 

FGTXYZADXYZGTYABC

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would result with 3,8

I have been interating through the string one char at a time using a while loop, but this take quite a bit of time. Is there a faster way?
Thank you for your time.

edited: Mon Aug 18 20:06:42 2003 by jeffa - formatting

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Re: nested pattern matching
by CombatSquirrel (Hermit) on Aug 18, 2003 at 19:14 UTC 
    perl -e "'FGTXYZGTFABCGHABC' =~ /[XYZ]{3}([A-Za-z]{0,21})[ABC]{3}/; 
         print $-[0] . ', ' . length($1);"
__OUTPUT__
3, 8

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    Note that the output for your first example is 3, 8 instead of 3, 3. The appropiate RegEx for that would have been /[XYZ]{3}([A-Za-z]{0,21}?)[ABC]{3}/ (non-greedy quantifiers).
    Hope this helped.
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      works great. Thanks. How would I put this into a while loop so I can traverse the whole string? Vince
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        This should do the trick: 
        #!perl

use strict;
use warnings;

my $string = qq[FGTXYZGTFABCGHABCFGTXYZADXYZGTYABC];

while ($string =~ /[XYZ]{3}([A-Za-z]{0,21}?)[ABC]{3}/g) {
   print $-[0] . ', ' . length($1) . $/;
}
__OUTPUT__
3, 3
20, 8

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        got it. Just added the //g at the end. Vince
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Re: nested pattern matching
by chromatic (Archbishop) on Aug 18, 2003 at 19:01 UTC

    I've never encountered such a problem, but could you use pos, capture the pattern, and use length on $1 to calculate what you need? You'd have to use the /g modifier, but I think it might work.

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