Match/Replace/Interpolate

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

Hello,

I am a bit stuck here in finding a way how to do this. I'm trying to match some value in some text to get a number <gid=1234>. I want to replace this tag with <img src="PATH/TO/$id"> where the $id will be the number I matched eg. 1234.

Matching and fetching the id is no problem, but trying to replace the correct entry gives me a hassle. Especially when there are more entries in one line.

Some example code:

use strict;

while (<DATA>) {
        my $line = $_;
        print $. . " " . $line;

        my @matches = /<gid=(\d+)>/g;

        foreach (@matches) {
                print "MATCH:: $_\n";
                $line =~ s/<gid=$1>/<img src="PATH\/TO\/$1>/
        }
        print "NEW" . $line;

}

__DATA__
<gid=3035>Wij zijn hier aan het moven. We gaan nog meer moven. <gid=30
+36>
Waarom wij dit doen weet ik ook niet. Maar we zullen het snel weten. <
+gid=3037>

<gid=3037>we testen dit zo.
[download]

--
My opinions may have changed,
but not the fact that I am right

Comment on Match/Replace/Interpolate Download Code

Replies are listed 'Best First'.
Re: Match/Replace/Interpolate by Corion (Patriarch) on Jul 21, 2006 at 08:38 UTC
I'd do the whole search-and-replace thing in one step instead of two steps: `$line =~ s!<gid=(\d+)>!<img src="PATH/TO/$1">!g;` [download] I think the only problem with your approach is that it lacked the `/g` "global" modifier that replaces all occurrences within one line. 20060721 shmem spotted a missing > sign, thanks!	[reply] [d/l] [select]
Re^2: Match/Replace/Interpolate by toadi (Chaplain) on Jul 21, 2006 at 08:58 UTC
Hi Corion, thanks for the reply. What do the ! mean instead of the normal / in the regex? -- My opinions may have changed, but not the fact that I am right	[reply]
Re^3: Match/Replace/Interpolate by Corion (Patriarch) on Jul 21, 2006 at 09:01 UTC
The `!` are used as alternative delimiters, because you use `/` within the regular expression. This makes it easy to avoid the escaping of slashes. Instead of `\/`, I now can write `/` as it will not be recognized as the regex delimiter anymore. perlop has the section on Regexp Quote-like Operators which explains how this works.	[reply] [d/l] [select]
Re^3: Match/Replace/Interpolate by gellyfish (Monsignor) on Jul 21, 2006 at 09:01 UTC
They don't mean anything special, you can replace the '/' with any other character (or matching pairs of brackets) to improve readability and reduce the requirement for escaping of literal '/' characters in your expression. /J\	[reply]
Re: Match/Replace/Interpolate by shmem (Chancellor) on Jul 21, 2006 at 09:35 UTC
Just a typo ($1 and $_). You mean: `$line =~ s/<gid=$_>/<img src="PATH\/TO\/$_>/` [download] --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l]