The value of $ur is "rba_Reset_Request".
foreach my $ur (@strings_to_be_matched)
{
     $reg1 = qr/\=/i;                 #line has a single '='
                                      #/i makes no difference, delete that!
                                      #there is no "capital ="!
     $reg2 = qr/\S+\=\S+/i;           #line has a single "=" with something
                                      #to the left and something to the right
     $reg3 = qr/extern.+\b$ur\b\s*/i; #line has extern rba_Reset_Request
     $reg4 = qr/;$/i;           #line ends in ";"  
                                # in C code you are not allowing for the
                                #idea that whitespace may be after the ";"
                                # /;\s*$/;
     $reg5 = qr/.+\b$ur\b\s*/i; #line has rba_Reset_Request
                                #could just be:
                                #/\b$ur\b/; ?

     foreach my $line (@contents_of_file)
{

     if(($ln =~ $reg3 and $ln =~ $reg4)){
     <some code>
     # line contains: extern rba_Reset_Request
     # and ends in a ;
     
     }

     if(($ln =~ $reg5 and $ln=~ $reg4 and ($ln !~ $reg1 or $ln =~ $reg2))
     {
     # line contains rba_Reset_Request, ends in a ";", has an "=" sign.
     
     <some code>
     }
     

     if(($ln =~ $reg3 and $ln !~ $reg4)){
     # line contains extern rba_Reset_Request and doesn't end in ;
     <some code>
     }

     if(($ln =~ $reg5 and $ln !~ $reg4 and $ln !~ $reg1))
     
     #line contains rba_Reset_Request doesn't end in ; or
     # have an = sign
     
     {
     <some code>
     }

   }
}