$file = <FILE>;

##</code><code>##

local $/ = undef;  
$file = <FILE>;

##</code><code>##

$file = join("", <FILE>);

##</code><code>##

foreach $this_paragraph (@paras) { 
  ....
}

##</code><code>##

foreach my $this_paragraph (@paras) {
  my @split_para = split(/:/, $this_paragraph);
  if( $split_para[1] = $KWD ) {
    print $this_paragraph;
  }
}

##</code><code>##

foreach my $this_paragraph (@paras) {
  if( $this_paragraph =~ /^$KWD:/s ) { 
    print $this_paragraph;
    # This works if the paragraph looks like 'KEYWORD: ...'
  }
}

##</code><code>##

foreach my $this_paragraph (@paras) {
  if( $this_paragraph =~ /:$KWD\b/s ) { 
    print $this_paragraph;
    # This works if the paragraph looks like '.... :KEYWORD ...'
  }
}