#!usr/bin/perl
use strict;
use warnings;
my $fpath = shift @ARGV;
open (my $fh, '<', $fpath) || die "Failed to open $fpath : $!";
my $matches = 0; ## counter for how many matches we have made
while (<$fh>){
  if ( /^(filename\s\"LKTA_mic)  ## find start of name and capture it
        \d+  ## number bit - don't capture
        (\.cfg\"\;\s\}$) ## end bit - capture
       /gx ){
    ## print out line with number modified based on how many matches we have seen
    print "$1".(($matches % 4) + 1)."$2\n";
    ## increment match counter
    ++$matches;
  }
  else {
    ## didn't match so pump it straight out unmodified
    print $line;
  }
};
close $fh || die "Failed to close $fpath : $!";