Connection Culv=This is Line1
     111 111 
Conn Culvert Barrel=Culvert1 
* 
Connection Culv=This is Line2 
     222 222 
Conn Culvert Barrel=Culvert2 
* 
Connection Culv=This is Line3 
     333 333 
Conn Culvert Barrel=Culvert3 
*
##</code><code>##

Connection Culv=This is Line3 - New text here 
     333 333 This should be new too 
Conn Culvert Barrel=Culvert3 
* 
Connection Culv=This is Line1 - New text here 
     111 111 This should be new too 
Conn Culvert Barrel=Culvert1 
* 
Connection Culv=This is Line2 - New text here 
     222 222 This should be new too 
Conn Culvert Barrel=Culvert2 
* 
##</code><code>##

Connection Culv=This is Line1 - New text here 
     111 111 
Conn Culvert Barrel=Culvert1 
* 
Connection Culv=This is Line2 - New text here 
     222 222 
Conn Culvert Barrel=Culvert2 
* 
Connection Culv=This is Line3 - New text here 
     333 333 
Conn Culvert Barrel=Culvert3 
* 
##</code><code>##

Connection Culv=This is Line1 - New text here 
     111 111 This should be new too
Conn Culvert Barrel=Culvert1 
* 
Connection Culv=This is Line2 - New text here 
     222 222 This should be new too
Conn Culvert Barrel=Culvert2 
* 
Connection Culv=This is Line3 - New text here 
     333 333 This should be new too
Conn Culvert Barrel=Culvert3 
* 
##</code><code>##

# HEC-RAS Replacement Perl Script
# This will find and replace values in the HEC-RAS geometry file for modified culvet barrels. The process is:
#    1. In existing model file (HECRAS_Ex.txt) find where there is a "Connection Culv" (this is the line that needs to be replaced)
#    2. It then down for the next Conn Culvert Barrel line (this is the unique identifier)
#    3. It then takes from the new culvert file (culvNEW.txt) the new "Connection Culv" line and replaces it in the existing HECRAS_Ex.txt file. 
#    4. Repeats for all and then saves out Output_HECRAS.txt

# Nomenclature for running Perl Script:
	# C:\MyDir> perl PERL_SCRIPT.pl culvNEW.txt HECRAS_Ex.txt OutPut_HECRAS.txt
	
# Read Existing HEC-RAS Geometry File (HECRAS_Ex) with Old Culvert Connection Attributes
open (TEMPLATE,  @ARGV[1]) or die;
@HECRAS_Ex = <TEMPLATE>;
close TEMPLATE;
	
# Read New Culvert Data File (culvNEW) with new Connection culvert Attributes
open (TEMPLATE, @ARGV[0]) or die;
@culvNEW = <TEMPLATE>;
close TEMPLATE;

for ($i=0; $i<@HECRAS_Ex; $i++) {

# only check lines starting with "Connection Culv" in the HECRAS_Ex file
   if ($HECRAS_Ex[$i] =~ /^Connection Culv/) {
		#print $HECRAS_Ex[$i];
		#look for Connection Culv backwards
      $iback=$i-1;
      while ($HECRAS_Ex[$iback] !~ /^Conn Culvert Barrel/) {
            $iback=$iback+1;
      }
      $local0=$HECRAS_Ex[$iback];
      chomp($local0);
			# print $HECRAS_Ex[$iback];
      for ($j=0; $j<@culvNEW; $j++) {
			# for ($j=0; $j<1; $j++) {
         $local = $culvNEW[$j];
         chomp($local);
			# print $local;
			# Remove the trailing new line
			# chomp $local;
			# print ($local eq $HECRAS_Ex[$iback]);
         if ($local =~ /^$local0/) {
			# print "match";
            $jforward=$j-1;
            while ($culvNEW[$jforward] !~ /^Connection Culv/) {
                  $jforward=$jforward-1;
                  }
			# print $culvNEW[$jforward];
            # Perform substitutions of LG card
              $HECRAS_Ex[$i]=$culvNEW[$jforward];
			# print $HECRAS_Ex[$i];
         }
      }
   }
}
#write out the Geometry File based on the HECRAS_Ex file structure and the new values in the culvNEW file
open (OUT, ">" . @ARGV[2]) or die;
# Write output
print OUT @HECRAS_Ex;
# Close OUT
close OUT;