Perl Cd Bookshelf [Electronic resources] نسخه متنی

Evaluates whether expr is a blessed
reference. If successful, blessed returns the name
of the package. Otherwise, blessed returns
undef.

use Scalar::Util qw(blessed);
use CGI;
my $cgi = CGI->new();
my $not_cgi = "IamNotCGI";
my $is_blessed = blessed($cgi);
if(defined($is_blessed) { print "$cgi\n;" } # Prints CGI
my $is_blessed2 = blessed($not_cgi);
if(defined($is_blessed2) { print "$not_cgi\n"; } # undef

Returns a string that has the value numberin a numeric context and a value string in
a string context. For example:

my $context = dualvar(10, "Nathan");
my $add_nums = $context + 1; # '11'
my $str_add = $context . "Patwardhan"; # Nathan Patwardhan

Returns true if expr is a scalar, which is
a weak reference:

my $weak_ref = \$boo_hoo;
my $i_am_weak = isweak($weak_ref); # false
weaken($weak_ref);
$i_am_weak = isweak($weak_ref); # true

Returns fh if fh is an
open filehandle. fh may also be a tied
filehandle. Returns undef on failure.

my $fh = openhandle(*STDIN);
$fh = openhandle("sumfin"); # undef, since sumfin isn't
# open

Returns true if scalar is read-only.

Returns the reference type of expr if expr is
a reference. Otherwise, returns undef.

my $r_type = reftype "ORA"; # undef, not a reference
my $r_type = reftype []; # ARRAY

Returns true if the result of expr is
tainted:

my $is_tainted = tainted($ENV{PATH});
# Returns true if -T is enabled

Returns ref into a weak reference. When
the reference count on an object reaches 0,
ref will be set to
undef.

8.179. Safe		8.181. SDBM_File