#!/usr/bin/perl

#this are a couple of example
$_ = <<'REGEXP';
$one = CONSTANT . 'string' . $obj->new[0] . $variable . "string" . $obj->method("some".'thing'.$more);

$some->method(
CONSTANT . $obj->new[0] . 'string' . $obj->method("some".'thing'.$more). $variable .  "string"
,
 "NOT INCLUDED"
);

sub(
CONSTANT . 'string' . $obj->new[0] . $variable . "string" . $obj->method("some".'thing'.$more)
);

REGEXP

#let's magic begin!
while (/

CONSTANT # begin the search with this string

   (?>  #start looking but not return if fails
        "[^"]*" # catch every thing within double quotes
           |    # or

        '[^']*' # catch every thing within single quotes
           |    # or

        (\(     # if its a parentheses 
            (?> #start looking but not return if fails
               [^()]++ # catch every thing that is not a parentheses
                |      # or
               (?1)    # if its a parentheses make a recursion in it
             )
         \))+

           |    #or same as above but looking square braket

        (\[     # if its a square braket
            (?> #start looking but not return if fails
               [^\[\]]++ # catch every thing that is not a square braket
                |      # or
               (?2)    # if its a square braket make a recursion in it
             )
         \])+

           |     # or

           [a-zA-Z0-9_.\-\>\s\$]++ #looking only this string "." is point

           |     # or

           (?R) # if those individual regexp fails, make a recursion,
                # only stop when all fails
     )*
/xgo) {
    print "$&\n";
}