{
    local $/; # slurp in a file
    my $contents = <$fh>
    ...
}

# now we go back to reading a file line-by-line again

while (<$fh>){
   ...
}
[download]

Parenthetic note: in the quoted example code, the  $fh file handle would become "exhausted" after the "slurp" read to  $contents and the subsequent while-loop read of the handle would produce nothing. A seek operation is needed to reset the logical file position back to the beginning of the file (update: or at least to somewhere other than the end) so that subsequent reads may be successful. Try the following code without the seek statement:

c:\@Work\Perl\monks\pmpmmpmp>perl -wMstrict -le
"open my $fh, '<', 'junk.txt' or die $!;
 ;;
 my $contents = do { local $/;  <$fh>; };
 print qq{[[$contents]]};
 ;;
 seek $fh, 0, 0;
 print 'now we go back to reading a file line-by-line again';
 while (<$fh>){
   print qq{<<$_>>};
   }
"
[[line 1 fee fie foe
line 2 wibble wobble
line 3 blah yada
]]
now we go back to reading a file line-by-line again
<<line 1 fee fie foe
>>
<<line 2 wibble wobble
>>
<<line 3 blah yada
>>
[download]