Update: Hah! Brother Athanasius is nimbler of finger (not to mention grey matter) ...

As Corion points out, <MYFILE> is a filehandle from which you read and process one line at a time; it doesn't represent a line itself. A corrected version of your code is below.

[00:28][nick:~/monks]$ cat 1139778.txt
foo
bar
baz
qux
[download]

#!/usr/bin/perl
use strict;
use warnings;

# Don't hard-code filenames in logic code
my $file = '1139778.txt';

# Use the three-argument form of open() ...
open( my $MYFILE, '<', $file )   
  or die "Failed to open $file: $!\n";     # ... and always check for 
+success

# Use parentheses to show we want the whole list of lines
my $data = join '', (<$MYFILE>); 
print "Using \$data:\n$data\n\n";

# Go back to the beginning of the file
seek $MYFILE, 0, 0;

# No parentheses so we get one line at a time
print "Using \$line:\n";
while ( my $line = <$MYFILE> )  {
  # chomp; # No need to chomp if you are printing the file out again
  print $line;
}

close $MYFILE or die "Failed to close $file: $!\n";

__END__
[download]

Output:

[00:29][nick:~/monks]$ perl 1139778.pl
Using $data:
foo
bar
baz
qux


Using $line:
foo
bar
baz
qux
[download]

Hope this helps! Make sure you understand it all before you continue :-)