my $slurp = join $/, <FH>;

##</code><code>##

#!/usr/bin/perl -w

use Benchmark qw(cmpthese);

# file.txt is about 2200 lines each between 5 and 50 chars long
open FH, "file.txt" or die $!;

sub scalarcon {
  seek(FH,0,0);
  local $/;
  <FH>;
}

sub listjoin {
  seek(FH,0,0);
  join '',<FH>;
}

cmpthese(-5,{scalarcon=>\&scalarcon,listjoin=>\&listjoin});
__DATA__
Benchmark: running listjoin, scalarcon for at least 5 CPU seconds...
  listjoin:  5 wallclock secs ( 5.25 usr +  0.12 sys =  5.38 CPU) @ 30.70/s (n=165)
 scalarcon:  6 wallclock secs ( 1.95 usr +  3.36 sys =  5.30 CPU) @ 153.26/s (n=813)
            Rate  listjoin scalarcon
listjoin  30.7/s        --      -80%
scalarcon  153/s      399%        --