how to find multiple regex patterns in a single way using Perl - perl

Question

Question Updated
I have list of (few more) regex patterns like: (Note: Sequence is very Important)
([a-z]+)(\d+)
\}([a-z]+)
([a-z]+)(\+|\-)
([0-9])\](\+|\-)
...
...
my input file like :
\ce{CO2}
\ce{2CO}
\ce{H2O}
\ce{Sb2O3}
...
...
In my code I am finding the each and every regex patterns like
if($string=~m/([a-z]+)(\d+)/g) { my statements ... }
if($string=~m/\}([a-z]+)/g) { my statements ... }
if($string=~m/([a-z]+)(\+|\-)/g) { my statements ... }
if($string=~m/([0-9])\](\+|\-)/g) { my statements ... }
Instead of doing the above code Is there any other way to simplify the code?
Could you someone please share your thoughts for my improvement for better coding.

Answer 1

Disclaimer: Your question is very hard to read, so this is pretty much guesswork. I am not sure I understand what you want to do.
When you are processing data in a dynamic way, a typical approach is to use a dispatch table. We can do something similar here. Often a hash or hash reference is used for that, but since we want a specific order, I will be using an array instead.
my #dispatch = (
{
pattern => qr/f(o)(o)/,
callback => sub {
my ($one, $two) = #_;
print "Found $one and $two\n";
},
},
{
pattern => qr/(bar)/,
callback => sub {
my $capture = shift;
print "Saw $capture";
},
},
);
This basically is a list of search patterns and associated instructions. Each pattern has a callback, which is a code reference. I decided it would make sense to pass in the capture variables, because your patterns have capture groups.
Now in order to call them, we iterate over the dispatch array, match the pattern and then call the associated callback, passing in all the captures.
my $text = "Foo bar foo bar baz.";
foreach my $search (#dispatch) {
if ($text =~ $search->{pattern}) {
$search->{callback}->(#{^CAPTURE}); # this requires Perl 5.26
}
}
Please note that I am using #{^CAPTURE}, which was added to Perl in version 5.25.7, so you would require at least the stable Perl 5.26 release to use it. (On an older Perl, my #capture = $t =~ $search->{pattern} and $search->{callback}->(#capture) will behave similarly).
This is way more elegant than having a list of if () {} statement because it's very easy to extend. The dispatch table could be created on the fly, based on some input, or entirely read from disk.
When we run this code, it creates the following output
Found o and o
Saw bar
This is not very spectacular, but you should be able to adapt it to your patterns. On the other hand I don't know what you are actually trying to do. If you wanted to modify the string instead of only matching, you might need additional arguments for your callbacks.
If you want to learn more about dispatch tables, I suggest you read the second chapter of Mark Jason Dominus' excellent book Higher Order Perl, which is available for free as a PDF on his website.

Answer 2

Your question is hard to read, mainly because you have the /g at the end of your regex searches (which returns a list), however, you only check if it matches once.
I'm making the following assumptions
All matches are required
the code can be a single or double match
both groups captured in one line
i think you want
while ( $string =~ /(([a-z]+)(\d+)|\}([a-z]+)|([a-z]+)(\+|\-)|([0-9])\](\+|\-))/g )
{
#$1 has the whole match
#$2 has the first group if defined
#$3 has the second group if defined
}
However, I prefer the method below. this will capture in one line
while ($string =~ /([a-z]+\d+|\}[a-z]+|[a-z]+\+|\-|[0-9]\]\+|\-)/g )
{
# in here split the match if required
}
I recommend you use regex comments to make this clearer.
if you just want a single match, use
if(
$string=~m/([a-z]+)(\d+)/ ||
$string=~m/\}([a-z]+)/ ||
$string=~m/([a-z]+)(\+|\-)/ ||
$string=~m/([0-9])\](\+|\-)/
)
{
#some code
}