use warnings;
use strict;

open (my $fh, '<', 'test.txt') || die "Failed to open test input : $!";
my $contents = '';
my $previous = 'Not set';
my $pass = 0;

while (<$fh>){
  my $line = $_;
  if ( $line =~ /^Content:/ && $previous =~ /^Subject:/ ){
    ## if we matched the previous line as a 'Subject' line
    ## and this line is a 'Content' line
    print $contents;
    $pass = 1;
    last;
  }
  
  ## append current line and set previous line
  $contents .= $line;
  $previous = $line;
}
print "No match found.\n" unless $pass;
close $fh || die "Failed to close test file : $!";