Extracting an element forming part of a variable in a regexp

[Gadhadhar]

I am developing a tool currently in Perl, and I need to extract characters from a variable that I put in a regexp. I illustrate directly, it will be clearer.

my $req = 'select machine from device where machine = $1';

my $separator = "\$";

my $variable = "foo";

$1 is not a variable, but the separator followed by the numeral "1". The separator is intended to be replaced by the variable thereafter that it contains in a string. I put "foo" for example. I then have the following regexp:

$req =~ s/\Q$sep/$var/;

print "reqfinal = $req\n"; # select code from client where code = foo1

This makes it possible to replace my separator variable. But what I also do is extract the "1" in a variable that I can use later, and also make sure to have that:

# select code from client where code = toto

in my result, without the "1" then.

[CitricAcid]

#!/usr/bin/perl
use strict;
use warnings;
my $req = 'select code from client where code = $1';
my $sep = '\$';
my $var = "foo"; 
if ($req =~ m/(.*?)$sep(\d+)/){
	$req = $1.$var;
	my $num = $2;
	print "req : $req\tnum = $num\n";
	# req : select code from client where code = foo	num = 1
}

[Gadhadhar]

It looks pretty good, but I can not make it work. Or rather, the print is blank, despite the fact that the code is good. Can I get more information about the code specially:

if ($req =~ m/(.*?)$sep(\d+)/){

For "select code from client where code ="?

I know the operation of each, but I do not know how well together they work.

[CitricAcid]

Search of

(.*?)$sep(\d+)

.*? any character from 0 to x times "select code from client where code = "

The question mark is used to make non-greedy search (in this instance, it is useless but I used to use with .*).

followed by $sep $

followed by \d+ of 1 to x digits 1

Parentheses are used to retrieve data in $1 and $2

It does something that you do not understand?

[Gadhadhar]

I admit that it was mainly the use of "?" who challenged me, thinking that ".*" is enough. I understand the rest. Thank you very much, it should work even if my display is failing yet. I reported there after debugging, once it is operational. So for now, it does not work. It does not gives me the contents if (the prints).

I fear that the contents of "$sep" is the character "$" does not involve the end of the string, and suddenly my game is not verified, not only making the contents of if.

Any idea?

Actually, when I put anything other than a dollar separator, such as "%" for example, the regexp works. I would therefore resolve the particular case of the "$" as a separator.

[CitricAcid]

In my code that I gave you works well with the $. And also if used with single quotes?

my $sep = '\$';

If you leave the double quotes open when you initialize the variable, backslash is deleted.