The code you have is correct, although fglock gives you a simpler and more idiomatic way to do it.

#!/usr/bin/perl -w

use strict;

my %h = (1 => "one",
     2 => "two");
%h = (%h, 3, "three");
%h = (%h, 4, "four");

print "h is:\n",printhash(%h);

sub printhash
{
  my $i = 0;
  join("",map { $_.($i++%2?"\n":" => ") } @_);
}
[download]

produces

h is:
1 => one
2 => two
3 => three
4 => four

Consider using debugging information to see if your error is elsewhere---for example, printing out the contents of $file and $text whenever you add to the hash.