use strict;
use warnings;

my $file = shift;

my $undefinedVars = 0;

open(FILE,$file);

while (<FILE>) {
  if (/(\$[^\/\n\t]*)/) {
    my $var = $&;
    my $key = $var;
    substr($key, 0, 1) = "";
    my $val = $ENV{$key};
    if (defined($val)) {
      my $line = $_;
      $line =~ s/\$//g;
      $line =~ s/$key/$val/g;
      print $line;
    } else {
      $undefinedVars++;
    }
  } else {
    print $_;
  }
}

close(FILE);

if ($undefinedVars > 0) {
  print "ERROR: There were $undefinedVars undefined variables!\n";
}