use File::Copy;
use strict;
my (@col, $val, $i);
open(COL, "<replace.txt");

while(<COL>) {
    push @col, $_ =~ m/(.*?):/;
}
close(COL);

open(OUT, ">out.txt");
open(COL, "<original.txt");
while(<COL>) {
    ($val) = $_ =~ m/(.*?):/;
    $_ =~ s/(.*?)(?=:)/$col[$i++]/ unless $val =~ m/^\s*$/;
    print OUT $_;
}
close(COL);
close(OUT);
copy("out.txt", "original.txt");